diff --git a/messages.pot b/messages.pot
index a4fc61d..7e14675 100644
--- a/messages.pot
+++ b/messages.pot
@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PROJECT VERSION\n"
 "Report-Msgid-Bugs-To: EMAIL@ADDRESS\n"
-"POT-Creation-Date: 2021-09-10 09:01+0200\n"
+"POT-Creation-Date: 2021-09-19 16:31+0200\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -191,7 +191,7 @@ msgstr ""
 msgid "Legal notice"
 msgstr ""
 
-#: project/forms/admin.py:12 project/templates/_macros.html:1389
+#: project/forms/admin.py:12 project/templates/_macros.html:1405
 #: project/templates/layout.html:313
 #: project/templates/widget/event_suggestion/create.html:204
 #: project/views/admin_unit.py:36 project/views/root.py:58
@@ -279,7 +279,7 @@ msgid "Longitude"
 msgstr ""
 
 #: project/forms/admin_unit.py:28 project/forms/event.py:36
-#: project/forms/event.py:65 project/forms/event.py:379
+#: project/forms/event.py:65 project/forms/event.py:399
 #: project/forms/event_place.py:25 project/forms/event_place.py:50
 #: project/forms/event_suggestion.py:26 project/forms/oauth2_client.py:66
 #: project/forms/organizer.py:25 project/forms/organizer.py:52
@@ -299,7 +299,7 @@ msgstr ""
 msgid "The short name is used to create a unique identifier for your events"
 msgstr ""
 
-#: project/forms/admin_unit.py:40 project/templates/_macros.html:1525
+#: project/forms/admin_unit.py:40 project/templates/_macros.html:1541
 msgid "Short name must contain only letters numbers or underscore"
 msgstr ""
 
@@ -313,7 +313,7 @@ msgstr ""
 #: project/forms/admin_unit_member.py:23 project/forms/admin_unit_member.py:28
 #: project/forms/event.py:58 project/forms/event_suggestion.py:38
 #: project/forms/organizer.py:27 project/templates/_macros.html:262
-#: project/templates/_macros.html:1485 project/templates/admin/users.html:19
+#: project/templates/_macros.html:1501 project/templates/admin/users.html:19
 msgid "Email"
 msgstr ""
 
@@ -492,8 +492,8 @@ msgstr ""
 msgid "All-day"
 msgstr ""
 
-#: project/forms/event.py:86 project/templates/event/create.html:252
-#: project/templates/event/update.html:143
+#: project/forms/event.py:86 project/templates/event/create.html:274
+#: project/templates/event/update.html:165
 #: project/templates/widget/event_suggestion/create.html:240
 msgid "Recurring event"
 msgstr ""
@@ -650,16 +650,16 @@ msgid ""
 " course it works without it."
 msgstr ""
 
-#: project/forms/event.py:208 project/templates/_macros.html:1246
+#: project/forms/event.py:208 project/templates/_macros.html:1262
 msgid "The start must be before the end."
 msgstr ""
 
-#: project/forms/event.py:214 project/templates/_macros.html:1263
+#: project/forms/event.py:214 project/templates/_macros.html:1279
 msgid "An event can last a maximum of 14 days."
 msgstr ""
 
 #: project/forms/event.py:222 project/templates/_macros.html:419
-#: project/templates/_macros.html:575
+#: project/templates/_macros.html:582
 msgid "Previous start date"
 msgstr ""
 
@@ -677,8 +677,8 @@ msgstr ""
 
 #: project/forms/event.py:235 project/forms/reference.py:14
 #: project/forms/reference.py:27 project/forms/reference_request.py:76
-#: project/templates/event/create.html:366
-#: project/templates/event/update.html:223
+#: project/templates/event/create.html:390
+#: project/templates/event/update.html:246
 msgid "Rating"
 msgstr ""
 
@@ -689,152 +689,166 @@ msgid ""
 "visible and is used for sorting."
 msgstr ""
 
-#: project/forms/event.py:247 project/forms/event.py:256
-#: project/forms/event.py:325 project/forms/event_suggestion.py:50
-#: project/templates/_macros.html:459 project/templates/_macros.html:612
-#: project/templates/event/create.html:291
-#: project/templates/event/update.html:173
+#: project/forms/event.py:244
+msgid "Co-organizers"
+msgstr ""
+
+#: project/forms/event.py:247
+msgid ""
+"Select optional co-organizers. You can add and modify organizers at "
+"Organization > Organizers."
+msgstr ""
+
+#: project/forms/event.py:258
+msgid "Invalid co-organizer."
+msgstr ""
+
+#: project/forms/event.py:267 project/forms/event.py:276
+#: project/forms/event.py:345 project/forms/event_suggestion.py:50
+#: project/templates/_macros.html:459 project/templates/_macros.html:619
+#: project/templates/event/create.html:315
+#: project/templates/event/update.html:196
 #: project/templates/event_place/create.html:31
 #: project/templates/event_place/delete.html:13
 #: project/templates/event_place/update.html:31
 msgid "Place"
 msgstr ""
 
-#: project/forms/event.py:249
+#: project/forms/event.py:269
 msgid "Select existing place"
 msgstr ""
 
-#: project/forms/event.py:250
+#: project/forms/event.py:270
 msgid "Enter new place"
 msgstr ""
 
-#: project/forms/event.py:263 project/forms/event.py:272
-#: project/forms/event.py:333 project/forms/event.py:395
-#: project/forms/event_suggestion.py:60 project/templates/_macros.html:497
-#: project/templates/_macros.html:649 project/templates/event/create.html:262
-#: project/templates/event/update.html:164
+#: project/forms/event.py:283 project/forms/event.py:292
+#: project/forms/event.py:353 project/forms/event.py:415
+#: project/forms/event_suggestion.py:60 project/templates/_macros.html:496
+#: project/templates/_macros.html:656 project/templates/event/create.html:284
+#: project/templates/event/update.html:186
 #: project/templates/organizer/create.html:27
 #: project/templates/organizer/delete.html:13
 #: project/templates/organizer/update.html:27
 msgid "Organizer"
 msgstr ""
 
-#: project/forms/event.py:265
+#: project/forms/event.py:285
 msgid "Select existing organizer"
 msgstr ""
 
-#: project/forms/event.py:266
+#: project/forms/event.py:286
 msgid "Enter new organizer"
 msgstr ""
 
-#: project/forms/event.py:278
+#: project/forms/event.py:298
 msgid "Save as draft"
 msgstr ""
 
-#: project/forms/event.py:279
+#: project/forms/event.py:299
 msgid "Publish event"
 msgstr ""
 
-#: project/forms/event.py:309
+#: project/forms/event.py:329
 msgid "Select existing place or enter new place"
 msgstr ""
 
-#: project/forms/event.py:316
+#: project/forms/event.py:336
 msgid "Select existing organizer or enter new organizer"
 msgstr ""
 
-#: project/forms/event.py:328
+#: project/forms/event.py:348
 msgid ""
 "Choose where the event takes place. You can add and modify places at "
-"Manage > Places."
+"Organization > Places."
 msgstr ""
 
-#: project/forms/event.py:336
+#: project/forms/event.py:356
 msgid ""
-"Select the organizer. You can add and modify organizers at Manage > "
-"Organizers."
+"Select the organizer. You can add and modify organizers at Organization >"
+" Organizers."
 msgstr ""
 
-#: project/forms/event.py:342 project/templates/event/update.html:153
+#: project/forms/event.py:362 project/templates/event/update.html:175
 #: project/templates/oauth2_token/list.html:21
 msgid "Status"
 msgstr ""
 
-#: project/forms/event.py:345
+#: project/forms/event.py:365
 msgid "EventStatus.scheduled"
 msgstr ""
 
-#: project/forms/event.py:346 project/templates/layout.html:82
+#: project/forms/event.py:366 project/templates/layout.html:82
 #: project/templates/layout.html:97
 msgid "EventStatus.cancelled"
 msgstr ""
 
-#: project/forms/event.py:347 project/templates/layout.html:85
+#: project/forms/event.py:367 project/templates/layout.html:85
 #: project/templates/layout.html:100
 msgid "EventStatus.movedOnline"
 msgstr ""
 
-#: project/forms/event.py:348 project/templates/layout.html:88
+#: project/forms/event.py:368 project/templates/layout.html:88
 #: project/templates/layout.html:103
 msgid "EventStatus.postponed"
 msgstr ""
 
-#: project/forms/event.py:349 project/templates/layout.html:91
+#: project/forms/event.py:369 project/templates/layout.html:91
 #: project/templates/layout.html:106
 msgid "EventStatus.rescheduled"
 msgstr ""
 
-#: project/forms/event.py:351
+#: project/forms/event.py:371
 msgid "Select the status of the event."
 msgstr ""
 
-#: project/forms/event.py:355
+#: project/forms/event.py:375
 msgid "Public status"
 msgstr ""
 
-#: project/forms/event.py:358
+#: project/forms/event.py:378
 msgid "PublicStatus.published"
 msgstr ""
 
-#: project/forms/event.py:359 project/templates/_macros.html:282
+#: project/forms/event.py:379 project/templates/_macros.html:282
 msgid "PublicStatus.draft"
 msgstr ""
 
-#: project/forms/event.py:361
+#: project/forms/event.py:381
 msgid "Select the public status of the event."
 msgstr ""
 
-#: project/forms/event.py:364 project/templates/event/update.html:5
-#: project/templates/event/update.html:119
+#: project/forms/event.py:384 project/templates/event/update.html:5
+#: project/templates/event/update.html:141
 msgid "Update event"
 msgstr ""
 
-#: project/forms/event.py:378 project/templates/_macros.html:1218
+#: project/forms/event.py:398 project/templates/_macros.html:1234
 #: project/templates/event/actions.html:47
 #: project/templates/event/delete.html:6
 msgid "Delete event"
 msgstr ""
 
-#: project/forms/event.py:386 project/forms/event_date.py:15
+#: project/forms/event.py:406 project/forms/event_date.py:15
 #: project/forms/planing.py:14
 msgid "From"
 msgstr ""
 
-#: project/forms/event.py:388 project/forms/event_date.py:17
+#: project/forms/event.py:408 project/forms/event_date.py:17
 #: project/forms/planing.py:16
 msgid "to"
 msgstr ""
 
-#: project/forms/event.py:390 project/forms/event_date.py:19
+#: project/forms/event.py:410 project/forms/event_date.py:19
 msgid "Keyword"
 msgstr ""
 
-#: project/forms/event.py:392 project/forms/event_date.py:21
+#: project/forms/event.py:412 project/forms/event_date.py:21
 #: project/forms/planing.py:19 project/templates/_macros.html:392
 msgid "Category"
 msgstr ""
 
-#: project/forms/event.py:398
+#: project/forms/event.py:418
 msgid "Find events"
 msgstr ""
 
@@ -895,13 +909,13 @@ msgstr ""
 msgid "I would like to be notified by email after the review"
 msgstr ""
 
-#: project/forms/event_suggestion.py:52 project/templates/event/create.html:296
+#: project/forms/event_suggestion.py:52 project/templates/event/create.html:320
 msgid ""
 "Choose where the event takes place. If the venue is not yet in the list, "
 "just enter it."
 msgstr ""
 
-#: project/forms/event_suggestion.py:62 project/templates/event/create.html:266
+#: project/forms/event_suggestion.py:62 project/templates/event/create.html:288
 msgid ""
 "Select the organizer. If the organizer is not yet on the list, just enter"
 " it."
@@ -983,7 +997,7 @@ msgid "Weekdays"
 msgstr ""
 
 #: project/forms/reference.py:11 project/forms/reference_request.py:16
-#: project/templates/_macros.html:518 project/templates/_macros.html:675
+#: project/templates/_macros.html:512 project/templates/_macros.html:672
 #: project/templates/admin_unit/create.html:28
 #: project/templates/admin_unit/update.html:29
 #: project/templates/layout.html:258
@@ -1011,7 +1025,7 @@ msgstr ""
 msgid "Delete request"
 msgstr ""
 
-#: project/forms/reference_request.py:28 project/templates/_macros.html:1401
+#: project/forms/reference_request.py:28 project/templates/_macros.html:1417
 #: project/templates/event_suggestion/review_status.html:18
 #: project/templates/reference_request/review_status.html:12
 msgid "Review status"
@@ -1078,7 +1092,7 @@ msgid "This field is required."
 msgstr ""
 
 #: project/templates/_macros.html:134 project/templates/_macros.html:414
-#: project/templates/_macros.html:914
+#: project/templates/_macros.html:930
 msgid "Date"
 msgstr ""
 
@@ -1118,64 +1132,64 @@ msgstr ""
 msgid "Last updated at %(updated_at)s."
 msgstr ""
 
-#: project/templates/_macros.html:408 project/templates/_macros.html:571
+#: project/templates/_macros.html:408 project/templates/_macros.html:578
 #: project/templates/event/actions.html:12
-#: project/templates/event/create.html:235
+#: project/templates/event/create.html:257
 #: project/templates/event/delete.html:13
-#: project/templates/event/update.html:126
+#: project/templates/event/update.html:148
 #: project/templates/widget/event_suggestion/create.html:229
 msgid "Event"
 msgstr ""
 
-#: project/templates/_macros.html:441 project/templates/_macros.html:593
-#: project/templates/_macros.html:1470 project/templates/event/actions.html:32
+#: project/templates/_macros.html:441 project/templates/_macros.html:600
+#: project/templates/_macros.html:1486 project/templates/event/actions.html:32
 msgid "Share"
 msgstr ""
 
-#: project/templates/_macros.html:445 project/templates/_macros.html:597
-#: project/templates/_macros.html:1500
+#: project/templates/_macros.html:445 project/templates/_macros.html:604
+#: project/templates/_macros.html:1516
 msgid "Add to calendar"
 msgstr ""
 
-#: project/templates/_macros.html:453 project/templates/_macros.html:605
+#: project/templates/_macros.html:453 project/templates/_macros.html:612
 #: project/templates/event/report.html:4
 msgid "Report event"
 msgstr ""
 
-#: project/templates/_macros.html:480 project/templates/_macros.html:631
+#: project/templates/_macros.html:480 project/templates/_macros.html:638
 msgid "Show directions"
 msgstr ""
 
-#: project/templates/_macros.html:485 project/templates/_macros.html:636
+#: project/templates/_macros.html:485 project/templates/_macros.html:643
 msgid "The event takes place online."
 msgstr ""
 
-#: project/templates/_macros.html:487 project/templates/_macros.html:638
+#: project/templates/_macros.html:487 project/templates/_macros.html:645
 msgid "The event takes place both offline and online."
 msgstr ""
 
-#: project/templates/_macros.html:699 project/templates/event_date/list.html:5
+#: project/templates/_macros.html:696 project/templates/event_date/list.html:5
 #: project/templates/event_date/list.html:300
 #: project/templates/event_date/search.html:3
 #: project/templates/reference_request/review.html:32
 msgid "Event Dates"
 msgstr ""
 
-#: project/templates/_macros.html:772
+#: project/templates/_macros.html:788
 msgid "Search location on Google"
 msgstr ""
 
-#: project/templates/_macros.html:838
+#: project/templates/_macros.html:854
 #, python-format
 msgid "%(count)d event dates"
 msgstr ""
 
-#: project/templates/_macros.html:854 project/templates/_macros.html:856
+#: project/templates/_macros.html:870 project/templates/_macros.html:872
 #: project/templates/event_date/list.html:321
 msgid "First"
 msgstr ""
 
-#: project/templates/_macros.html:859 project/templates/_macros.html:861
+#: project/templates/_macros.html:875 project/templates/_macros.html:877
 #: project/templates/event_date/list.html:322
 #: project/templates/widget/event_suggestion/create.html:193
 #: project/templates/widget/event_suggestion/create.html:218
@@ -1186,12 +1200,12 @@ msgstr ""
 msgid "Previous"
 msgstr ""
 
-#: project/templates/_macros.html:863
+#: project/templates/_macros.html:879
 #, python-format
 msgid "Page %(page)d of %(pages)d (%(total)d total)"
 msgstr ""
 
-#: project/templates/_macros.html:865 project/templates/_macros.html:867
+#: project/templates/_macros.html:881 project/templates/_macros.html:883
 #: project/templates/event_date/list.html:324
 #: project/templates/widget/event_suggestion/create.html:194
 #: project/templates/widget/event_suggestion/create.html:219
@@ -1201,73 +1215,73 @@ msgstr ""
 msgid "Next"
 msgstr ""
 
-#: project/templates/_macros.html:870 project/templates/_macros.html:872
+#: project/templates/_macros.html:886 project/templates/_macros.html:888
 #: project/templates/event_date/list.html:325
 msgid "Last"
 msgstr ""
 
-#: project/templates/_macros.html:937
+#: project/templates/_macros.html:953
 msgid "Radius"
 msgstr ""
 
-#: project/templates/_macros.html:1147
+#: project/templates/_macros.html:1163
 msgid "Edit image"
 msgstr ""
 
-#: project/templates/_macros.html:1168
+#: project/templates/_macros.html:1184
 msgid "Close"
 msgstr ""
 
-#: project/templates/_macros.html:1169
+#: project/templates/_macros.html:1185
 msgid "Okay"
 msgstr ""
 
-#: project/templates/_macros.html:1181
+#: project/templates/_macros.html:1197
 msgid "Choose image file"
 msgstr ""
 
-#: project/templates/_macros.html:1217 project/templates/event/actions.html:46
+#: project/templates/_macros.html:1233 project/templates/event/actions.html:46
 msgid "Edit event"
 msgstr ""
 
-#: project/templates/_macros.html:1220 project/templates/manage/events.html:40
+#: project/templates/_macros.html:1236 project/templates/manage/events.html:40
 msgid "More"
 msgstr ""
 
-#: project/templates/_macros.html:1267
+#: project/templates/_macros.html:1283
 msgid "Please enter a valid time, between 00:00 and 23:59."
 msgstr ""
 
-#: project/templates/_macros.html:1295
+#: project/templates/_macros.html:1311
 #, python-format
 msgid "Just use %(term)s"
 msgstr ""
 
-#: project/templates/_macros.html:1361
+#: project/templates/_macros.html:1377
 msgid "Event suggestion"
 msgstr ""
 
-#: project/templates/_macros.html:1479
+#: project/templates/_macros.html:1495
 msgid "Link copied"
 msgstr ""
 
-#: project/templates/_macros.html:1479
+#: project/templates/_macros.html:1495
 msgid "Copy link"
 msgstr ""
 
-#: project/templates/_macros.html:1508
+#: project/templates/_macros.html:1524
 msgid "Google calendar"
 msgstr ""
 
-#: project/templates/_macros.html:1509
+#: project/templates/_macros.html:1525
 msgid "Apple calendar"
 msgstr ""
 
-#: project/templates/_macros.html:1510
+#: project/templates/_macros.html:1526
 msgid "Yahoo calendar"
 msgstr ""
 
-#: project/templates/_macros.html:1511
+#: project/templates/_macros.html:1527
 msgid "Other calendar"
 msgstr ""
 
@@ -1327,7 +1341,7 @@ msgid "Show events"
 msgstr ""
 
 #: project/templates/event/create.html:5
-#: project/templates/event/create.html:228 project/templates/layout.html:226
+#: project/templates/event/create.html:250 project/templates/layout.html:226
 #: project/templates/manage/events.html:22
 #: project/templates/manage/organizers.html:21
 msgid "Create event"
@@ -1444,8 +1458,8 @@ msgstr ""
 
 #: project/templates/admin_unit/create.html:58
 #: project/templates/admin_unit/update.html:59
-#: project/templates/event/create.html:354
-#: project/templates/event/update.html:211
+#: project/templates/event/create.html:378
+#: project/templates/event/update.html:234
 #: project/templates/event_place/create.html:57
 #: project/templates/event_place/update.html:57
 #: project/templates/organizer/create.html:56
@@ -1570,31 +1584,33 @@ msgid "Enter place or address"
 msgstr ""
 
 #: project/templates/event/create.html:183
+#: project/templates/event/create.html:240
 #: project/templates/event/update.html:106
+#: project/templates/event/update.html:132
 #: project/templates/widget/event_suggestion/create.html:129
 msgid "Enter organizer"
 msgstr ""
 
-#: project/templates/event/create.html:245
-#: project/templates/event/update.html:136
+#: project/templates/event/create.html:267
+#: project/templates/event/update.html:158
 msgid "Event date"
 msgstr ""
 
-#: project/templates/event/create.html:283
+#: project/templates/event/create.html:305
 msgid "Switch to organizer search"
 msgstr ""
 
-#: project/templates/event/create.html:316
+#: project/templates/event/create.html:340
 msgid "Switch to place search"
 msgstr ""
 
-#: project/templates/event/create.html:327
-#: project/templates/event/update.html:184
+#: project/templates/event/create.html:351
+#: project/templates/event/update.html:207
 msgid "Access"
 msgstr ""
 
-#: project/templates/event/create.html:341
-#: project/templates/event/update.html:198
+#: project/templates/event/create.html:365
+#: project/templates/event/update.html:221
 msgid "Target group"
 msgstr ""
 
@@ -1900,11 +1916,11 @@ msgstr ""
 msgid "Event successfully deleted"
 msgstr ""
 
-#: project/views/event.py:397
+#: project/views/event.py:404
 msgid "Referenced event changed"
 msgstr ""
 
-#: project/views/event.py:420
+#: project/views/event.py:427
 msgid "New event report"
 msgstr ""
 
diff --git a/migrations/versions/811e16ed3bf0_.py b/migrations/versions/811e16ed3bf0_.py
new file mode 100644
index 0000000..9181899
--- /dev/null
+++ b/migrations/versions/811e16ed3bf0_.py
@@ -0,0 +1,61 @@
+"""empty message
+
+Revision ID: 811e16ed3bf0
+Revises: 12ca023b94f8
+Create Date: 2021-09-18 16:21:08.415884
+
+"""
+import sqlalchemy as sa
+import sqlalchemy_utils
+from alembic import op
+
+from project import dbtypes
+
+# revision identifiers, used by Alembic.
+revision = "811e16ed3bf0"
+down_revision = "12ca023b94f8"
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.create_table(
+        "event_coorganizers",
+        sa.Column("id", sa.Integer(), nullable=False),
+        sa.Column("event_id", sa.Integer(), nullable=False),
+        sa.Column("organizer_id", sa.Integer(), nullable=False),
+        sa.ForeignKeyConstraint(
+            ["event_id"],
+            ["event.id"],
+        ),
+        sa.ForeignKeyConstraint(
+            ["organizer_id"],
+            ["eventorganizer.id"],
+        ),
+        sa.PrimaryKeyConstraint("id"),
+        sa.UniqueConstraint("event_id", "organizer_id"),
+    )
+    op.create_unique_constraint(
+        "event_eventcategories_event_id_category_id",
+        "event_eventcategories",
+        ["event_id", "category_id"],
+    )
+    op.create_unique_constraint(
+        "eventsuggestion_eventcategories_event_suggestion_id_category_id",
+        "eventsuggestion_eventcategories",
+        ["event_suggestion_id", "category_id"],
+    )
+
+
+def downgrade():
+    op.drop_constraint(
+        "eventsuggestion_eventcategories_event_suggestion_id_category_id",
+        "eventsuggestion_eventcategories",
+        type_="unique",
+    )
+    op.drop_constraint(
+        "event_eventcategories_event_id_category_id",
+        "event_eventcategories",
+        type_="unique",
+    )
+    op.drop_table("event_coorganizers")
diff --git a/project/api/event/schemas.py b/project/api/event/schemas.py
index a011346..415144f 100644
--- a/project/api/event/schemas.py
+++ b/project/api/event/schemas.py
@@ -16,7 +16,11 @@ from project.api.image.schemas import (
     ImageSchema,
 )
 from project.api.organization.schemas import OrganizationRefSchema
-from project.api.organizer.schemas import OrganizerRefSchema, OrganizerWriteIdSchema
+from project.api.organizer.schemas import (
+    OrganizerDumpIdSchema,
+    OrganizerRefSchema,
+    OrganizerWriteIdSchema,
+)
 from project.api.place.schemas import (
     PlaceRefSchema,
     PlaceSearchItemSchema,
@@ -167,6 +171,7 @@ class EventSchema(EventIdSchema, EventBaseSchemaMixin):
     place = fields.Nested(PlaceRefSchema, attribute="event_place")
     photo = fields.Nested(ImageSchema)
     categories = fields.List(fields.Nested(EventCategoryRefSchema))
+    co_organizers = fields.List(fields.Nested(OrganizerRefSchema))
 
 
 class EventDumpSchema(EventIdSchema, EventBaseSchemaMixin):
@@ -177,6 +182,9 @@ class EventDumpSchema(EventIdSchema, EventBaseSchemaMixin):
     category_ids = fields.Pluck(
         EventCategoryIdSchema, "id", many=True, attribute="categories"
     )
+    co_organizer_ids = fields.Pluck(
+        OrganizerDumpIdSchema, "id", many=True, attribute="co_organizers"
+    )
 
 
 class EventRefSchema(EventIdSchema):
@@ -262,6 +270,10 @@ class EventWriteSchemaMixin(object):
         required=True,
         metadata={"description": "Who is organizing the event."},
     )
+    co_organizers = fields.List(
+        fields.Nested(OrganizerWriteIdSchema),
+        metadata={"description": "Optional co-organizers."},
+    )
     place = fields.Nested(
         PlaceWriteIdSchema,
         required=True,
diff --git a/project/api/organizer/schemas.py b/project/api/organizer/schemas.py
index a4bb1f3..b164e93 100644
--- a/project/api/organizer/schemas.py
+++ b/project/api/organizer/schemas.py
@@ -31,6 +31,10 @@ class OrganizerIdSchema(OrganizerModelSchema, IdSchemaMixin):
     pass
 
 
+class OrganizerDumpIdSchema(OrganizerModelSchema, IdSchemaMixin):
+    pass
+
+
 class OrganizerWriteIdSchema(OrganizerModelSchema, WriteIdSchemaMixin):
     pass
 
diff --git a/project/cli/test.py b/project/cli/test.py
index 4006585..f396e5c 100644
--- a/project/cli/test.py
+++ b/project/cli/test.py
@@ -2,6 +2,7 @@ import json
 
 import click
 from flask.cli import AppGroup
+from flask_migrate import stamp
 from flask_security.confirmable import confirm_user
 from sqlalchemy import MetaData
 
@@ -97,6 +98,7 @@ def drop_all():
 
 @test_cli.command("create-all")
 def create_all():
+    stamp()
     db.create_all()
     click.echo("Create all done.")
 
diff --git a/project/forms/event.py b/project/forms/event.py
index d7e0964..f33ccc5 100644
--- a/project/forms/event.py
+++ b/project/forms/event.py
@@ -240,6 +240,25 @@ class BaseEventForm(SharedEventForm):
             "Choose how relevant the event is to your organization. The value is not visible and is used for sorting."
         ),
     )
+    co_organizer_ids = SelectMultipleField(
+        lazy_gettext("Co-organizers"),
+        validators=[Optional()],
+        coerce=int,
+        description=lazy_gettext(
+            "Select optional co-organizers. You can add and modify organizers at Organization > Organizers."
+        ),
+    )
+
+    def validate(self):
+        result = super().validate()
+
+        if self.co_organizer_ids.data and self.organizer_id.data:
+            if self.organizer_id.data in self.co_organizer_ids.data:
+                msg = gettext("Invalid co-organizer.")
+                self.co_organizer_ids.errors.append(msg)
+                result = False
+
+        return result
 
 
 class CreateEventForm(BaseEventForm):
@@ -301,7 +320,7 @@ class CreateEventForm(BaseEventForm):
         )
 
     def validate(self):
-        if not super(BaseEventForm, self).validate():
+        if not super().validate():
             return False
         if (
             not self.event_place_id.data or self.event_place_id.data == 0
@@ -326,7 +345,7 @@ class UpdateEventForm(BaseEventForm):
         validators=[DataRequired()],
         coerce=int,
         description=lazy_gettext(
-            "Choose where the event takes place. You can add and modify places at Manage > Places."
+            "Choose where the event takes place. You can add and modify places at Organization > Places."
         ),
     )
     organizer_id = SelectField(
@@ -334,7 +353,7 @@ class UpdateEventForm(BaseEventForm):
         validators=[DataRequired()],
         coerce=int,
         description=lazy_gettext(
-            "Select the organizer. You can add and modify organizers at Manage > Organizers."
+            "Select the organizer. You can add and modify organizers at Organization > Organizers."
         ),
     )
 
diff --git a/project/jsonld.py b/project/jsonld.py
index 7d43626..d493e2f 100644
--- a/project/jsonld.py
+++ b/project/jsonld.py
@@ -133,8 +133,13 @@ def get_sd_for_event_date(event_date):
     result["location"] = get_sd_for_place(event.event_place)
 
     organizer_list = list()
+
     if event.organizer:
         organizer_list.append(get_sd_for_organizer(event.organizer))
+
+    for co_organizer in event.co_organizers:
+        organizer_list.append(get_sd_for_organizer(co_organizer))
+
     if event.admin_unit:
         organizer_list.append(get_sd_for_admin_unit(event.admin_unit))
     result["organizer"] = organizer_list
diff --git a/project/models.py b/project/models.py
index 161fb5a..a80f57a 100644
--- a/project/models.py
+++ b/project/models.py
@@ -331,6 +331,12 @@ class AdminUnitRelation(db.Model, TrackableMixin):
             raise make_check_violation("There must be no self-reference.")
 
 
+@listens_for(AdminUnitRelation, "before_insert")
+@listens_for(AdminUnitRelation, "before_update")
+def before_saving_admin_unit_relation(mapper, connect, self):
+    self.validate()
+
+
 class AdminUnit(db.Model, TrackableMixin):
     __tablename__ = "adminunit"
     id = Column(Integer(), primary_key=True)
@@ -765,6 +771,11 @@ class Event(db.Model, TrackableMixin, EventMixin):
     event_place = db.relationship("EventPlace", uselist=False)
 
     categories = relationship("EventCategory", secondary="event_eventcategories")
+    co_organizers = relationship(
+        "EventOrganizer",
+        secondary="event_coorganizers",
+        backref=backref("co_organized_events", lazy=True),
+    )
 
     public_status = Column(
         IntegerEnum(PublicStatus),
@@ -798,12 +809,30 @@ class Event(db.Model, TrackableMixin, EventMixin):
         else:
             return None
 
+    @property
+    def co_organizer_ids(self):
+        return [c.id for c in self.co_organizers]
+
+    @co_organizer_ids.setter
+    def co_organizer_ids(self, value):
+        self.co_organizers = EventOrganizer.query.filter(
+            EventOrganizer.id.in_(value)
+        ).all()
+
     def validate(self):
         if self.organizer and self.organizer.admin_unit_id != self.admin_unit_id:
-            raise make_check_violation("Invalid organizer")
+            raise make_check_violation("Invalid organizer.")
+
+        if self.co_organizers:
+            for co_organizer in self.co_organizers:
+                if (
+                    co_organizer.admin_unit_id != self.admin_unit_id
+                    or co_organizer.id == self.organizer_id
+                ):
+                    raise make_check_violation("Invalid co-organizer.")
 
         if self.event_place and self.event_place.admin_unit_id != self.admin_unit_id:
-            raise make_check_violation("Invalid place")
+            raise make_check_violation("Invalid place.")
 
         if self.start and self.end:
             if self.start > self.end:
@@ -816,7 +845,8 @@ class Event(db.Model, TrackableMixin, EventMixin):
 
 @listens_for(Event, "before_insert")
 @listens_for(Event, "before_update")
-def purge_event(mapper, connect, self):
+def before_saving_event(mapper, connect, self):
+    self.validate()
     self.purge_event_mixin()
 
 
@@ -842,6 +872,7 @@ def purge_event_date(mapper, connect, self):
 
 class EventEventCategories(db.Model):
     __tablename__ = "event_eventcategories"
+    __table_args__ = (UniqueConstraint("event_id", "category_id"),)
     id = Column(Integer(), primary_key=True)
     event_id = db.Column(db.Integer, db.ForeignKey("event.id"), nullable=False)
     category_id = db.Column(
@@ -851,6 +882,7 @@ class EventEventCategories(db.Model):
 
 class EventSuggestionEventCategories(db.Model):
     __tablename__ = "eventsuggestion_eventcategories"
+    __table_args__ = (UniqueConstraint("event_suggestion_id", "category_id"),)
     id = Column(Integer(), primary_key=True)
     event_suggestion_id = db.Column(
         db.Integer, db.ForeignKey("eventsuggestion.id"), nullable=False
@@ -860,6 +892,16 @@ class EventSuggestionEventCategories(db.Model):
     )
 
 
+class EventCoOrganizers(db.Model):
+    __tablename__ = "event_coorganizers"
+    __table_args__ = (UniqueConstraint("event_id", "organizer_id"),)
+    id = Column(Integer(), primary_key=True)
+    event_id = db.Column(db.Integer, db.ForeignKey("event.id"), nullable=False)
+    organizer_id = db.Column(
+        db.Integer, db.ForeignKey("eventorganizer.id"), nullable=False
+    )
+
+
 class Analytics(db.Model):
     __tablename__ = "analytics"
     id = Column(Integer(), primary_key=True)
diff --git a/project/templates/_macros.html b/project/templates/_macros.html
index a673151..cba8592 100644
--- a/project/templates/_macros.html
+++ b/project/templates/_macros.html
@@ -491,25 +491,19 @@
   </div>
 
   {% if event.organizer %}
-
   <div class="card mb-3">
     <div class="card-header">
       {{ _('Organizer') }}
     </div>
     <div class="card-body">
-          <h5 class="card-title">{{ render_string_prop(event.organizer.name) }}</h5>
-
-          {% if event.organizer.logo_id %}
-            <div class="my-4">{{ render_logo(event.organizer.logo) }}</div>
-          {% endif %}
-
-          {{ render_link_prop(event.organizer.url) }}
-          {{ render_email_prop(event.organizer.email) }}
-          {{ render_phone_prop(event.organizer.phone) }}
-          {{ render_fax_prop(event.organizer.fax) }}
+        {{ render_event_props_organizer(event.organizer) }}
+        {% for co_organizer in event.co_organizers %}
+          <div{% if loop.index > 0 %} class="mt-4"{% endif %}>
+            {{ render_event_props_organizer(co_organizer) }}
+          </div>
+        {% endfor %}
     </div>
   </div>
-
   {% endif %}
 
   {% if show_admin_unit %}
@@ -539,6 +533,19 @@
 
 {% endmacro %}
 
+{% macro render_event_props_organizer(organizer) %}
+<h5 class="card-title">{{ render_string_prop(organizer.name) }}</h5>
+
+{% if organizer.logo_id %}
+  <div class="my-4">{{ render_logo(organizer.logo) }}</div>
+{% endif %}
+
+{{ render_link_prop(organizer.url) }}
+{{ render_email_prop(organizer.email) }}
+{{ render_phone_prop(organizer.phone) }}
+{{ render_fax_prop(organizer.fax) }}
+{% endmacro %}
+
 {% macro render_event_props_seo(event, start, end, allday, dates = None, show_rating = False, show_admin_unit = True, user_rights=None, share_links=None, calendar_links=None) %}
 <div class="w-normal mx-auto">
 
@@ -648,22 +655,12 @@
     <div class="card-body">
       <h2 class="mt-0">{{ _('Organizer') }}</h2>
 
-      <div class="row">
-        {% if event.organizer.logo_id %}
-        <div class="col-12 col-sm-auto order-sm-last">{{ render_logo(event.organizer.logo) }}</div>
-        {% endif %}
-
-        <div class="col-12 col-sm">
-          <div class="font-weight-bold">
-            {{ render_string_prop(event.organizer.name) }}
-          </div>
-
-          {{ render_link_prop(event.organizer.url) }}
-          {{ render_email_prop(event.organizer.email) }}
-          {{ render_phone_prop(event.organizer.phone) }}
-          {{ render_fax_prop(event.organizer.fax) }}
+      {{ render_event_props_seo_organizer(event.organizer) }}
+      {% for co_organizer in event.co_organizers %}
+        <div{% if loop.index > 0 %} class="mt-4"{% endif %}>
+          {{ render_event_props_seo_organizer(co_organizer) }}
         </div>
-      </div>
+      {% endfor %}
     </div>
   </div>
 
@@ -710,6 +707,25 @@
 
 {% endmacro %}
 
+{% macro render_event_props_seo_organizer(organizer) %}
+<div class="row">
+  {% if organizer.logo_id %}
+  <div class="col-12 col-sm-auto order-sm-last">{{ render_logo(organizer.logo) }}</div>
+  {% endif %}
+
+  <div class="col-12 col-sm">
+    <div class="font-weight-bold">
+      {{ render_string_prop(organizer.name) }}
+    </div>
+
+    {{ render_link_prop(organizer.url) }}
+    {{ render_email_prop(organizer.email) }}
+    {{ render_phone_prop(organizer.phone) }}
+    {{ render_fax_prop(organizer.fax) }}
+  </div>
+</div>
+{% endmacro %}
+
 {% macro render_google_place_autocomplete_header() %}
 <script>
   $( function() {
diff --git a/project/templates/event/create.html b/project/templates/event/create.html
index 8fb35f3..ad2583f 100644
--- a/project/templates/event/create.html
+++ b/project/templates/event/create.html
@@ -218,6 +218,28 @@ $( function() {
 
   update_organizer_container($('input[type=radio][name=organizer_choice]:checked').val());
 
+  $('#co_organizer_ids').select2({
+      width: '100%',
+      ajax: {
+        url: "{{ url_for('api_v1_organization_organizer_list', id=admin_unit.id) }}",
+        dataType: 'json',
+        delay: 250,
+        cache: true,
+        data: function (params) {
+          return {
+            name: params.term,
+            per_page: 5
+          };
+        },
+        processResults: function (data) {
+          return {
+            results: data.items.map(p => ({"id": p.id, "text": p.name}))
+          };
+        }
+      },
+      placeholder: "{{ _('Enter organizer') }}"
+    });
+
   {{ render_end_container_handling() }}
 
 });
@@ -283,6 +305,8 @@ $( function() {
           <a href="#" id="new_organizer_container_search_link"><i class="fa fa-search"></i> {{ _('Switch to organizer search') }}</a>
         </div>
       </div>
+
+      {{ render_field_with_errors(form.co_organizer_ids, class="w-100") }}
     </div>
   </div>
 
diff --git a/project/templates/event/update.html b/project/templates/event/update.html
index d0bf410..fa84e95 100644
--- a/project/templates/event/update.html
+++ b/project/templates/event/update.html
@@ -110,6 +110,28 @@
           $(this).valid();
       });
 
+      $('#co_organizer_ids').select2({
+        width: '100%',
+        ajax: {
+          url: "{{ url_for('api_v1_organization_organizer_list', id=event.admin_unit.id) }}",
+          dataType: 'json',
+          delay: 250,
+          cache: true,
+          data: function (params) {
+            return {
+              name: params.term,
+              per_page: 5
+            };
+          },
+          processResults: function (data) {
+            return {
+              results: data.items.map(p => ({"id": p.id, "text": p.name}))
+            };
+          }
+        },
+        placeholder: "{{ _('Enter organizer') }}"
+      });
+
       {{ render_end_container_handling() }}
     });
   </script>
@@ -165,6 +187,7 @@
     </div>
     <div class="card-body pb-0">
       {{ render_field_with_errors(form.organizer_id, class="w-100", label_hidden=True) }}
+      {{ render_field_with_errors(form.co_organizer_ids, class="w-100") }}
     </div>
   </div>
 
diff --git a/project/translations/de/LC_MESSAGES/messages.mo b/project/translations/de/LC_MESSAGES/messages.mo
index dbdbcd5..d583785 100644
Binary files a/project/translations/de/LC_MESSAGES/messages.mo and b/project/translations/de/LC_MESSAGES/messages.mo differ
diff --git a/project/translations/de/LC_MESSAGES/messages.po b/project/translations/de/LC_MESSAGES/messages.po
index c5aff84..cd5c71d 100644
--- a/project/translations/de/LC_MESSAGES/messages.po
+++ b/project/translations/de/LC_MESSAGES/messages.po
@@ -7,7 +7,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PROJECT VERSION\n"
 "Report-Msgid-Bugs-To: EMAIL@ADDRESS\n"
-"POT-Creation-Date: 2021-09-10 09:01+0200\n"
+"POT-Creation-Date: 2021-09-19 16:31+0200\n"
 "PO-Revision-Date: 2020-06-07 18:51+0200\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language: de\n"
@@ -192,7 +192,7 @@ msgstr "Nutzungsbedingungen"
 msgid "Legal notice"
 msgstr "Impressum"
 
-#: project/forms/admin.py:12 project/templates/_macros.html:1389
+#: project/forms/admin.py:12 project/templates/_macros.html:1405
 #: project/templates/layout.html:313
 #: project/templates/widget/event_suggestion/create.html:204
 #: project/views/admin_unit.py:36 project/views/root.py:58
@@ -284,7 +284,7 @@ msgid "Longitude"
 msgstr "Längengrad"
 
 #: project/forms/admin_unit.py:28 project/forms/event.py:36
-#: project/forms/event.py:65 project/forms/event.py:379
+#: project/forms/event.py:65 project/forms/event.py:399
 #: project/forms/event_place.py:25 project/forms/event_place.py:50
 #: project/forms/event_suggestion.py:26 project/forms/oauth2_client.py:66
 #: project/forms/organizer.py:25 project/forms/organizer.py:52
@@ -307,7 +307,7 @@ msgstr ""
 "eindeutig zu identifizieren. Der Kurzname darf nur Buchstaben, Nummern "
 "und Unterstriche enthalten."
 
-#: project/forms/admin_unit.py:40 project/templates/_macros.html:1525
+#: project/forms/admin_unit.py:40 project/templates/_macros.html:1541
 msgid "Short name must contain only letters numbers or underscore"
 msgstr "Der Kurzname darf nur Buchstaben, Nummern und Unterstriche enthalten"
 
@@ -321,7 +321,7 @@ msgstr "Link URL"
 #: project/forms/admin_unit_member.py:23 project/forms/admin_unit_member.py:28
 #: project/forms/event.py:58 project/forms/event_suggestion.py:38
 #: project/forms/organizer.py:27 project/templates/_macros.html:262
-#: project/templates/_macros.html:1485 project/templates/admin/users.html:19
+#: project/templates/_macros.html:1501 project/templates/admin/users.html:19
 msgid "Email"
 msgstr "Email"
 
@@ -505,8 +505,8 @@ msgstr ""
 msgid "All-day"
 msgstr "Ganztägig"
 
-#: project/forms/event.py:86 project/templates/event/create.html:252
-#: project/templates/event/update.html:143
+#: project/forms/event.py:86 project/templates/event/create.html:274
+#: project/templates/event/update.html:165
 #: project/templates/widget/event_suggestion/create.html:240
 msgid "Recurring event"
 msgstr "Regelmäßige Veranstaltung"
@@ -674,16 +674,16 @@ msgstr ""
 "Wir empfehlen dir, ein Foto für die Veranstaltung hochzuladen. Es macht "
 "schon deutlich mehr her, aber es geht natürlich auch ohne."
 
-#: project/forms/event.py:208 project/templates/_macros.html:1246
+#: project/forms/event.py:208 project/templates/_macros.html:1262
 msgid "The start must be before the end."
 msgstr "Der Start muss vor dem Ende sein."
 
-#: project/forms/event.py:214 project/templates/_macros.html:1263
+#: project/forms/event.py:214 project/templates/_macros.html:1279
 msgid "An event can last a maximum of 14 days."
 msgstr "Eine Veranstaltung darf maximal 14 Tage dauern."
 
 #: project/forms/event.py:222 project/templates/_macros.html:419
-#: project/templates/_macros.html:575
+#: project/templates/_macros.html:582
 msgid "Previous start date"
 msgstr "Vorheriges Startdatum"
 
@@ -703,8 +703,8 @@ msgstr "Wähle Kategorien, die zur Veranstaltung passen."
 
 #: project/forms/event.py:235 project/forms/reference.py:14
 #: project/forms/reference.py:27 project/forms/reference_request.py:76
-#: project/templates/event/create.html:366
-#: project/templates/event/update.html:223
+#: project/templates/event/create.html:390
+#: project/templates/event/update.html:246
 msgid "Rating"
 msgstr "Bewertung"
 
@@ -717,156 +717,172 @@ msgstr ""
 "Wähle aus, wie relevant die Veranstaltung für deine Organisation ist. Der"
 " Wert ist nicht sichtbar und dient der Sortierung."
 
-#: project/forms/event.py:247 project/forms/event.py:256
-#: project/forms/event.py:325 project/forms/event_suggestion.py:50
-#: project/templates/_macros.html:459 project/templates/_macros.html:612
-#: project/templates/event/create.html:291
-#: project/templates/event/update.html:173
+#: project/forms/event.py:244
+msgid "Co-organizers"
+msgstr "Mitveranstalter"
+
+#: project/forms/event.py:247
+msgid ""
+"Select optional co-organizers. You can add and modify organizers at "
+"Organization > Organizers."
+msgstr ""
+"Wähle optionale Mitveranstalter. Du kannst Veranstalter unter "
+"Organisation > Veranstalter hinzufügen und ändern."
+
+#: project/forms/event.py:258
+msgid "Invalid co-organizer."
+msgstr "Ungültiger Mitveranstalter."
+
+#: project/forms/event.py:267 project/forms/event.py:276
+#: project/forms/event.py:345 project/forms/event_suggestion.py:50
+#: project/templates/_macros.html:459 project/templates/_macros.html:619
+#: project/templates/event/create.html:315
+#: project/templates/event/update.html:196
 #: project/templates/event_place/create.html:31
 #: project/templates/event_place/delete.html:13
 #: project/templates/event_place/update.html:31
 msgid "Place"
 msgstr "Ort"
 
-#: project/forms/event.py:249
+#: project/forms/event.py:269
 msgid "Select existing place"
 msgstr "Vorhandenen Ort auswählen"
 
-#: project/forms/event.py:250
+#: project/forms/event.py:270
 msgid "Enter new place"
 msgstr "Neuen Ort eingeben"
 
-#: project/forms/event.py:263 project/forms/event.py:272
-#: project/forms/event.py:333 project/forms/event.py:395
-#: project/forms/event_suggestion.py:60 project/templates/_macros.html:497
-#: project/templates/_macros.html:649 project/templates/event/create.html:262
-#: project/templates/event/update.html:164
+#: project/forms/event.py:283 project/forms/event.py:292
+#: project/forms/event.py:353 project/forms/event.py:415
+#: project/forms/event_suggestion.py:60 project/templates/_macros.html:496
+#: project/templates/_macros.html:656 project/templates/event/create.html:284
+#: project/templates/event/update.html:186
 #: project/templates/organizer/create.html:27
 #: project/templates/organizer/delete.html:13
 #: project/templates/organizer/update.html:27
 msgid "Organizer"
 msgstr "Veranstalter"
 
-#: project/forms/event.py:265
+#: project/forms/event.py:285
 msgid "Select existing organizer"
 msgstr "Vorhandenen Veranstalter auswählen"
 
-#: project/forms/event.py:266
+#: project/forms/event.py:286
 msgid "Enter new organizer"
 msgstr "Neuen Veranstalter eingeben"
 
-#: project/forms/event.py:278
+#: project/forms/event.py:298
 msgid "Save as draft"
 msgstr "Als Entwurf speichern"
 
-#: project/forms/event.py:279
+#: project/forms/event.py:299
 msgid "Publish event"
 msgstr "Veranstaltung veröffentlichen"
 
-#: project/forms/event.py:309
+#: project/forms/event.py:329
 msgid "Select existing place or enter new place"
 msgstr "Existierenden Ort wählen oder neuen Ort eingeben"
 
-#: project/forms/event.py:316
+#: project/forms/event.py:336
 msgid "Select existing organizer or enter new organizer"
 msgstr "Wähle einen vorhandenen Veranstalter oder gib einen neuen Veranstalter ein"
 
-#: project/forms/event.py:328
+#: project/forms/event.py:348
 msgid ""
 "Choose where the event takes place. You can add and modify places at "
-"Manage > Places."
+"Organization > Places."
 msgstr ""
-"Wähle, wo die Veranstaltung stattfindet. Du kannst Orte unter Verwaltung "
-"> Orte hinzufügen und ändern."
+"Wähle, wo die Veranstaltung stattfindet. Du kannst Orte unter "
+"Organisation > Orte hinzufügen und ändern."
 
-#: project/forms/event.py:336
+#: project/forms/event.py:356
 msgid ""
-"Select the organizer. You can add and modify organizers at Manage > "
-"Organizers."
+"Select the organizer. You can add and modify organizers at Organization >"
+" Organizers."
 msgstr ""
-"Wähle den Veranstalter. Du kannst Veranstalter unter Verwaltung > "
+"Wähle den Veranstalter. Du kannst Veranstalter unter Organisation > "
 "Veranstalter hinzufügen und ändern."
 
-#: project/forms/event.py:342 project/templates/event/update.html:153
+#: project/forms/event.py:362 project/templates/event/update.html:175
 #: project/templates/oauth2_token/list.html:21
 msgid "Status"
 msgstr "Status"
 
-#: project/forms/event.py:345
+#: project/forms/event.py:365
 msgid "EventStatus.scheduled"
 msgstr "Geplant"
 
-#: project/forms/event.py:346 project/templates/layout.html:82
+#: project/forms/event.py:366 project/templates/layout.html:82
 #: project/templates/layout.html:97
 msgid "EventStatus.cancelled"
 msgstr "Abgesagt"
 
-#: project/forms/event.py:347 project/templates/layout.html:85
+#: project/forms/event.py:367 project/templates/layout.html:85
 #: project/templates/layout.html:100
 msgid "EventStatus.movedOnline"
 msgstr "Online verschoben"
 
-#: project/forms/event.py:348 project/templates/layout.html:88
+#: project/forms/event.py:368 project/templates/layout.html:88
 #: project/templates/layout.html:103
 msgid "EventStatus.postponed"
 msgstr "Verschoben"
 
-#: project/forms/event.py:349 project/templates/layout.html:91
+#: project/forms/event.py:369 project/templates/layout.html:91
 #: project/templates/layout.html:106
 msgid "EventStatus.rescheduled"
 msgstr "Neu angesetzt"
 
-#: project/forms/event.py:351
+#: project/forms/event.py:371
 msgid "Select the status of the event."
 msgstr "Wähle den Status der Veranstaltung."
 
-#: project/forms/event.py:355
+#: project/forms/event.py:375
 msgid "Public status"
 msgstr "Öffentlicher Status"
 
-#: project/forms/event.py:358
+#: project/forms/event.py:378
 msgid "PublicStatus.published"
 msgstr "Veröffentlicht"
 
-#: project/forms/event.py:359 project/templates/_macros.html:282
+#: project/forms/event.py:379 project/templates/_macros.html:282
 msgid "PublicStatus.draft"
 msgstr "Entwurf"
 
-#: project/forms/event.py:361
+#: project/forms/event.py:381
 msgid "Select the public status of the event."
 msgstr "Wähle den öffentlichen Status der Veranstaltung."
 
-#: project/forms/event.py:364 project/templates/event/update.html:5
-#: project/templates/event/update.html:119
+#: project/forms/event.py:384 project/templates/event/update.html:5
+#: project/templates/event/update.html:141
 msgid "Update event"
 msgstr "Veranstaltung aktualisieren"
 
-#: project/forms/event.py:378 project/templates/_macros.html:1218
+#: project/forms/event.py:398 project/templates/_macros.html:1234
 #: project/templates/event/actions.html:47
 #: project/templates/event/delete.html:6
 msgid "Delete event"
 msgstr "Veranstaltung löschen"
 
-#: project/forms/event.py:386 project/forms/event_date.py:15
+#: project/forms/event.py:406 project/forms/event_date.py:15
 #: project/forms/planing.py:14
 msgid "From"
 msgstr "Von"
 
-#: project/forms/event.py:388 project/forms/event_date.py:17
+#: project/forms/event.py:408 project/forms/event_date.py:17
 #: project/forms/planing.py:16
 msgid "to"
 msgstr "bis"
 
-#: project/forms/event.py:390 project/forms/event_date.py:19
+#: project/forms/event.py:410 project/forms/event_date.py:19
 msgid "Keyword"
 msgstr "Stichwort"
 
-#: project/forms/event.py:392 project/forms/event_date.py:21
+#: project/forms/event.py:412 project/forms/event_date.py:21
 #: project/forms/planing.py:19 project/templates/_macros.html:392
 msgid "Category"
 msgstr "Kategorie"
 
-#: project/forms/event.py:398
+#: project/forms/event.py:418
 msgid "Find events"
 msgstr "Veranstaltungen finden"
 
@@ -927,7 +943,7 @@ msgstr "Bitte gib deine Email-Adresse oder deine Telefonnummer für die Prüfung
 msgid "I would like to be notified by email after the review"
 msgstr "Ich möchte per Email benachrichtigt werden nach der Prüfung"
 
-#: project/forms/event_suggestion.py:52 project/templates/event/create.html:296
+#: project/forms/event_suggestion.py:52 project/templates/event/create.html:320
 msgid ""
 "Choose where the event takes place. If the venue is not yet in the list, "
 "just enter it."
@@ -935,7 +951,7 @@ msgstr ""
 "Wähle aus, wo die Veranstaltung stattfindet. Ist der Veranstaltungsort "
 "noch nicht in der Liste, trage ihn einfach ein."
 
-#: project/forms/event_suggestion.py:62 project/templates/event/create.html:266
+#: project/forms/event_suggestion.py:62 project/templates/event/create.html:288
 msgid ""
 "Select the organizer. If the organizer is not yet on the list, just enter"
 " it."
@@ -1019,7 +1035,7 @@ msgid "Weekdays"
 msgstr "Wochentage"
 
 #: project/forms/reference.py:11 project/forms/reference_request.py:16
-#: project/templates/_macros.html:518 project/templates/_macros.html:675
+#: project/templates/_macros.html:512 project/templates/_macros.html:672
 #: project/templates/admin_unit/create.html:28
 #: project/templates/admin_unit/update.html:29
 #: project/templates/layout.html:258
@@ -1047,7 +1063,7 @@ msgstr "Anfrage speichern"
 msgid "Delete request"
 msgstr "Anfrage löschen"
 
-#: project/forms/reference_request.py:28 project/templates/_macros.html:1401
+#: project/forms/reference_request.py:28 project/templates/_macros.html:1417
 #: project/templates/event_suggestion/review_status.html:18
 #: project/templates/reference_request/review_status.html:12
 msgid "Review status"
@@ -1114,7 +1130,7 @@ msgid "This field is required."
 msgstr "Dieses Feld ist erforderlich."
 
 #: project/templates/_macros.html:134 project/templates/_macros.html:414
-#: project/templates/_macros.html:914
+#: project/templates/_macros.html:930
 msgid "Date"
 msgstr "Datum"
 
@@ -1154,66 +1170,66 @@ msgstr "Zuletzt aktualisiert am %(updated_at)s von %(updated_by)s."
 msgid "Last updated at %(updated_at)s."
 msgstr "Zuletzt aktualisiert am %(updated_at)s."
 
-#: project/templates/_macros.html:408 project/templates/_macros.html:571
+#: project/templates/_macros.html:408 project/templates/_macros.html:578
 #: project/templates/event/actions.html:12
-#: project/templates/event/create.html:235
+#: project/templates/event/create.html:257
 #: project/templates/event/delete.html:13
-#: project/templates/event/update.html:126
+#: project/templates/event/update.html:148
 #: project/templates/widget/event_suggestion/create.html:229
 msgid "Event"
 msgstr "Veranstaltung"
 
-#: project/templates/_macros.html:441 project/templates/_macros.html:593
-#: project/templates/_macros.html:1470 project/templates/event/actions.html:32
+#: project/templates/_macros.html:441 project/templates/_macros.html:600
+#: project/templates/_macros.html:1486 project/templates/event/actions.html:32
 msgid "Share"
 msgstr "Teilen"
 
-#: project/templates/_macros.html:445 project/templates/_macros.html:597
-#: project/templates/_macros.html:1500
+#: project/templates/_macros.html:445 project/templates/_macros.html:604
+#: project/templates/_macros.html:1516
 msgid "Add to calendar"
 msgstr "Zum Kalender"
 
-#: project/templates/_macros.html:453 project/templates/_macros.html:605
+#: project/templates/_macros.html:453 project/templates/_macros.html:612
 #: project/templates/event/report.html:4
 msgid "Report event"
 msgstr "Veranstaltung melden"
 
-#: project/templates/_macros.html:480 project/templates/_macros.html:631
+#: project/templates/_macros.html:480 project/templates/_macros.html:638
 msgid "Show directions"
 msgstr "Anreise planen"
 
-#: project/templates/_macros.html:485 project/templates/_macros.html:636
+#: project/templates/_macros.html:485 project/templates/_macros.html:643
 msgid "The event takes place online."
 msgstr "Die Veranstaltung findet online statt."
 
-#: project/templates/_macros.html:487 project/templates/_macros.html:638
+#: project/templates/_macros.html:487 project/templates/_macros.html:645
 msgid "The event takes place both offline and online."
 msgstr ""
 "Die Veranstaltung findet sowohl als Präsenzveranstaltung als auch online "
 "statt."
 
-#: project/templates/_macros.html:699 project/templates/event_date/list.html:5
+#: project/templates/_macros.html:696 project/templates/event_date/list.html:5
 #: project/templates/event_date/list.html:300
 #: project/templates/event_date/search.html:3
 #: project/templates/reference_request/review.html:32
 msgid "Event Dates"
 msgstr "Termine"
 
-#: project/templates/_macros.html:772
+#: project/templates/_macros.html:788
 msgid "Search location on Google"
 msgstr "Ort bei Google suchen"
 
-#: project/templates/_macros.html:838
+#: project/templates/_macros.html:854
 #, python-format
 msgid "%(count)d event dates"
 msgstr "%(count)d Termine"
 
-#: project/templates/_macros.html:854 project/templates/_macros.html:856
+#: project/templates/_macros.html:870 project/templates/_macros.html:872
 #: project/templates/event_date/list.html:321
 msgid "First"
 msgstr "Letzte"
 
-#: project/templates/_macros.html:859 project/templates/_macros.html:861
+#: project/templates/_macros.html:875 project/templates/_macros.html:877
 #: project/templates/event_date/list.html:322
 #: project/templates/widget/event_suggestion/create.html:193
 #: project/templates/widget/event_suggestion/create.html:218
@@ -1224,12 +1240,12 @@ msgstr "Letzte"
 msgid "Previous"
 msgstr "Zurück"
 
-#: project/templates/_macros.html:863
+#: project/templates/_macros.html:879
 #, python-format
 msgid "Page %(page)d of %(pages)d (%(total)d total)"
 msgstr "Seite %(page)d von %(pages)d (%(total)d insgesamt)"
 
-#: project/templates/_macros.html:865 project/templates/_macros.html:867
+#: project/templates/_macros.html:881 project/templates/_macros.html:883
 #: project/templates/event_date/list.html:324
 #: project/templates/widget/event_suggestion/create.html:194
 #: project/templates/widget/event_suggestion/create.html:219
@@ -1239,73 +1255,73 @@ msgstr "Seite %(page)d von %(pages)d (%(total)d insgesamt)"
 msgid "Next"
 msgstr "Weiter"
 
-#: project/templates/_macros.html:870 project/templates/_macros.html:872
+#: project/templates/_macros.html:886 project/templates/_macros.html:888
 #: project/templates/event_date/list.html:325
 msgid "Last"
 msgstr "Erste"
 
-#: project/templates/_macros.html:937
+#: project/templates/_macros.html:953
 msgid "Radius"
 msgstr "Umkreis"
 
-#: project/templates/_macros.html:1147
+#: project/templates/_macros.html:1163
 msgid "Edit image"
 msgstr "Bild bearbeiten"
 
-#: project/templates/_macros.html:1168
+#: project/templates/_macros.html:1184
 msgid "Close"
 msgstr "Schließen"
 
-#: project/templates/_macros.html:1169
+#: project/templates/_macros.html:1185
 msgid "Okay"
 msgstr "OK"
 
-#: project/templates/_macros.html:1181
+#: project/templates/_macros.html:1197
 msgid "Choose image file"
 msgstr "Bild-Datei auswählen"
 
-#: project/templates/_macros.html:1217 project/templates/event/actions.html:46
+#: project/templates/_macros.html:1233 project/templates/event/actions.html:46
 msgid "Edit event"
 msgstr "Veranstaltung bearbeiten"
 
-#: project/templates/_macros.html:1220 project/templates/manage/events.html:40
+#: project/templates/_macros.html:1236 project/templates/manage/events.html:40
 msgid "More"
 msgstr "Mehr"
 
-#: project/templates/_macros.html:1267
+#: project/templates/_macros.html:1283
 msgid "Please enter a valid time, between 00:00 and 23:59."
 msgstr "Bitte gib eine gültige Uhrzeit zwischen 00:00 und 23:59 ein."
 
-#: project/templates/_macros.html:1295
+#: project/templates/_macros.html:1311
 #, python-format
 msgid "Just use %(term)s"
 msgstr "Verwende einfach %(term)s"
 
-#: project/templates/_macros.html:1361
+#: project/templates/_macros.html:1377
 msgid "Event suggestion"
 msgstr "Veranstaltungsvorschlag"
 
-#: project/templates/_macros.html:1479
+#: project/templates/_macros.html:1495
 msgid "Link copied"
 msgstr "Link kopiert"
 
-#: project/templates/_macros.html:1479
+#: project/templates/_macros.html:1495
 msgid "Copy link"
 msgstr "Link kopieren"
 
-#: project/templates/_macros.html:1508
+#: project/templates/_macros.html:1524
 msgid "Google calendar"
 msgstr "Google Kalender"
 
-#: project/templates/_macros.html:1509
+#: project/templates/_macros.html:1525
 msgid "Apple calendar"
 msgstr "Apple Kalender"
 
-#: project/templates/_macros.html:1510
+#: project/templates/_macros.html:1526
 msgid "Yahoo calendar"
 msgstr "Yahoo Kalender"
 
-#: project/templates/_macros.html:1511
+#: project/templates/_macros.html:1527
 msgid "Other calendar"
 msgstr "Anderer Kalender"
 
@@ -1365,7 +1381,7 @@ msgid "Show events"
 msgstr "Veranstaltungen anzeigen"
 
 #: project/templates/event/create.html:5
-#: project/templates/event/create.html:228 project/templates/layout.html:226
+#: project/templates/event/create.html:250 project/templates/layout.html:226
 #: project/templates/manage/events.html:22
 #: project/templates/manage/organizers.html:21
 msgid "Create event"
@@ -1482,8 +1498,8 @@ msgstr "Bearbeiten"
 
 #: project/templates/admin_unit/create.html:58
 #: project/templates/admin_unit/update.html:59
-#: project/templates/event/create.html:354
-#: project/templates/event/update.html:211
+#: project/templates/event/create.html:378
+#: project/templates/event/update.html:234
 #: project/templates/event_place/create.html:57
 #: project/templates/event_place/update.html:57
 #: project/templates/organizer/create.html:56
@@ -1610,31 +1626,33 @@ msgid "Enter place or address"
 msgstr "Orte oder Adresse eingeben"
 
 #: project/templates/event/create.html:183
+#: project/templates/event/create.html:240
 #: project/templates/event/update.html:106
+#: project/templates/event/update.html:132
 #: project/templates/widget/event_suggestion/create.html:129
 msgid "Enter organizer"
 msgstr "Veranstalter eingeben"
 
-#: project/templates/event/create.html:245
-#: project/templates/event/update.html:136
+#: project/templates/event/create.html:267
+#: project/templates/event/update.html:158
 msgid "Event date"
 msgstr "Termin"
 
-#: project/templates/event/create.html:283
+#: project/templates/event/create.html:305
 msgid "Switch to organizer search"
 msgstr "Zur Veranstaltersuche wechseln"
 
-#: project/templates/event/create.html:316
+#: project/templates/event/create.html:340
 msgid "Switch to place search"
 msgstr "Zur Ortssuche wechseln"
 
-#: project/templates/event/create.html:327
-#: project/templates/event/update.html:184
+#: project/templates/event/create.html:351
+#: project/templates/event/update.html:207
 msgid "Access"
 msgstr "Zugang"
 
-#: project/templates/event/create.html:341
-#: project/templates/event/update.html:198
+#: project/templates/event/create.html:365
+#: project/templates/event/update.html:221
 msgid "Target group"
 msgstr "Zielgruppe"
 
@@ -1943,11 +1961,11 @@ msgstr "Der eingegebene Name entspricht nicht dem Namen der Veranstaltung"
 msgid "Event successfully deleted"
 msgstr "Veranstaltung erfolgreich gelöscht"
 
-#: project/views/event.py:397
+#: project/views/event.py:404
 msgid "Referenced event changed"
 msgstr "Empfohlene Veranstaltung wurde geändert"
 
-#: project/views/event.py:420
+#: project/views/event.py:427
 msgid "New event report"
 msgstr "Neue Meldung zu einer Veranstaltung"
 
diff --git a/project/translations/en/LC_MESSAGES/messages.mo b/project/translations/en/LC_MESSAGES/messages.mo
index 824e6b0..b96d6be 100644
Binary files a/project/translations/en/LC_MESSAGES/messages.mo and b/project/translations/en/LC_MESSAGES/messages.mo differ
diff --git a/project/translations/en/LC_MESSAGES/messages.po b/project/translations/en/LC_MESSAGES/messages.po
index 555153a..9198fd0 100644
--- a/project/translations/en/LC_MESSAGES/messages.po
+++ b/project/translations/en/LC_MESSAGES/messages.po
@@ -7,7 +7,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PROJECT VERSION\n"
 "Report-Msgid-Bugs-To: EMAIL@ADDRESS\n"
-"POT-Creation-Date: 2021-09-10 09:01+0200\n"
+"POT-Creation-Date: 2021-09-19 16:31+0200\n"
 "PO-Revision-Date: 2021-04-30 15:04+0200\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language: en\n"
@@ -192,7 +192,7 @@ msgstr ""
 msgid "Legal notice"
 msgstr ""
 
-#: project/forms/admin.py:12 project/templates/_macros.html:1389
+#: project/forms/admin.py:12 project/templates/_macros.html:1405
 #: project/templates/layout.html:313
 #: project/templates/widget/event_suggestion/create.html:204
 #: project/views/admin_unit.py:36 project/views/root.py:58
@@ -280,7 +280,7 @@ msgid "Longitude"
 msgstr ""
 
 #: project/forms/admin_unit.py:28 project/forms/event.py:36
-#: project/forms/event.py:65 project/forms/event.py:379
+#: project/forms/event.py:65 project/forms/event.py:399
 #: project/forms/event_place.py:25 project/forms/event_place.py:50
 #: project/forms/event_suggestion.py:26 project/forms/oauth2_client.py:66
 #: project/forms/organizer.py:25 project/forms/organizer.py:52
@@ -300,7 +300,7 @@ msgstr ""
 msgid "The short name is used to create a unique identifier for your events"
 msgstr ""
 
-#: project/forms/admin_unit.py:40 project/templates/_macros.html:1525
+#: project/forms/admin_unit.py:40 project/templates/_macros.html:1541
 msgid "Short name must contain only letters numbers or underscore"
 msgstr ""
 
@@ -314,7 +314,7 @@ msgstr ""
 #: project/forms/admin_unit_member.py:23 project/forms/admin_unit_member.py:28
 #: project/forms/event.py:58 project/forms/event_suggestion.py:38
 #: project/forms/organizer.py:27 project/templates/_macros.html:262
-#: project/templates/_macros.html:1485 project/templates/admin/users.html:19
+#: project/templates/_macros.html:1501 project/templates/admin/users.html:19
 msgid "Email"
 msgstr ""
 
@@ -493,8 +493,8 @@ msgstr ""
 msgid "All-day"
 msgstr ""
 
-#: project/forms/event.py:86 project/templates/event/create.html:252
-#: project/templates/event/update.html:143
+#: project/forms/event.py:86 project/templates/event/create.html:274
+#: project/templates/event/update.html:165
 #: project/templates/widget/event_suggestion/create.html:240
 msgid "Recurring event"
 msgstr ""
@@ -651,16 +651,16 @@ msgid ""
 " course it works without it."
 msgstr ""
 
-#: project/forms/event.py:208 project/templates/_macros.html:1246
+#: project/forms/event.py:208 project/templates/_macros.html:1262
 msgid "The start must be before the end."
 msgstr ""
 
-#: project/forms/event.py:214 project/templates/_macros.html:1263
+#: project/forms/event.py:214 project/templates/_macros.html:1279
 msgid "An event can last a maximum of 14 days."
 msgstr ""
 
 #: project/forms/event.py:222 project/templates/_macros.html:419
-#: project/templates/_macros.html:575
+#: project/templates/_macros.html:582
 msgid "Previous start date"
 msgstr ""
 
@@ -678,8 +678,8 @@ msgstr ""
 
 #: project/forms/event.py:235 project/forms/reference.py:14
 #: project/forms/reference.py:27 project/forms/reference_request.py:76
-#: project/templates/event/create.html:366
-#: project/templates/event/update.html:223
+#: project/templates/event/create.html:390
+#: project/templates/event/update.html:246
 msgid "Rating"
 msgstr ""
 
@@ -690,152 +690,166 @@ msgid ""
 "visible and is used for sorting."
 msgstr ""
 
-#: project/forms/event.py:247 project/forms/event.py:256
-#: project/forms/event.py:325 project/forms/event_suggestion.py:50
-#: project/templates/_macros.html:459 project/templates/_macros.html:612
-#: project/templates/event/create.html:291
-#: project/templates/event/update.html:173
+#: project/forms/event.py:244
+msgid "Co-organizers"
+msgstr ""
+
+#: project/forms/event.py:247
+msgid ""
+"Select optional co-organizers. You can add and modify organizers at "
+"Organization > Organizers."
+msgstr ""
+
+#: project/forms/event.py:258
+msgid "Invalid co-organizer."
+msgstr ""
+
+#: project/forms/event.py:267 project/forms/event.py:276
+#: project/forms/event.py:345 project/forms/event_suggestion.py:50
+#: project/templates/_macros.html:459 project/templates/_macros.html:619
+#: project/templates/event/create.html:315
+#: project/templates/event/update.html:196
 #: project/templates/event_place/create.html:31
 #: project/templates/event_place/delete.html:13
 #: project/templates/event_place/update.html:31
 msgid "Place"
 msgstr ""
 
-#: project/forms/event.py:249
+#: project/forms/event.py:269
 msgid "Select existing place"
 msgstr ""
 
-#: project/forms/event.py:250
+#: project/forms/event.py:270
 msgid "Enter new place"
 msgstr ""
 
-#: project/forms/event.py:263 project/forms/event.py:272
-#: project/forms/event.py:333 project/forms/event.py:395
-#: project/forms/event_suggestion.py:60 project/templates/_macros.html:497
-#: project/templates/_macros.html:649 project/templates/event/create.html:262
-#: project/templates/event/update.html:164
+#: project/forms/event.py:283 project/forms/event.py:292
+#: project/forms/event.py:353 project/forms/event.py:415
+#: project/forms/event_suggestion.py:60 project/templates/_macros.html:496
+#: project/templates/_macros.html:656 project/templates/event/create.html:284
+#: project/templates/event/update.html:186
 #: project/templates/organizer/create.html:27
 #: project/templates/organizer/delete.html:13
 #: project/templates/organizer/update.html:27
 msgid "Organizer"
 msgstr ""
 
-#: project/forms/event.py:265
+#: project/forms/event.py:285
 msgid "Select existing organizer"
 msgstr ""
 
-#: project/forms/event.py:266
+#: project/forms/event.py:286
 msgid "Enter new organizer"
 msgstr ""
 
-#: project/forms/event.py:278
+#: project/forms/event.py:298
 msgid "Save as draft"
 msgstr ""
 
-#: project/forms/event.py:279
+#: project/forms/event.py:299
 msgid "Publish event"
 msgstr ""
 
-#: project/forms/event.py:309
+#: project/forms/event.py:329
 msgid "Select existing place or enter new place"
 msgstr ""
 
-#: project/forms/event.py:316
+#: project/forms/event.py:336
 msgid "Select existing organizer or enter new organizer"
 msgstr ""
 
-#: project/forms/event.py:328
+#: project/forms/event.py:348
 msgid ""
 "Choose where the event takes place. You can add and modify places at "
-"Manage > Places."
+"Organization > Places."
 msgstr ""
 
-#: project/forms/event.py:336
+#: project/forms/event.py:356
 msgid ""
-"Select the organizer. You can add and modify organizers at Manage > "
-"Organizers."
+"Select the organizer. You can add and modify organizers at Organization >"
+" Organizers."
 msgstr ""
 
-#: project/forms/event.py:342 project/templates/event/update.html:153
+#: project/forms/event.py:362 project/templates/event/update.html:175
 #: project/templates/oauth2_token/list.html:21
 msgid "Status"
 msgstr ""
 
-#: project/forms/event.py:345
+#: project/forms/event.py:365
 msgid "EventStatus.scheduled"
 msgstr "Scheduled"
 
-#: project/forms/event.py:346 project/templates/layout.html:82
+#: project/forms/event.py:366 project/templates/layout.html:82
 #: project/templates/layout.html:97
 msgid "EventStatus.cancelled"
 msgstr "Cancelled"
 
-#: project/forms/event.py:347 project/templates/layout.html:85
+#: project/forms/event.py:367 project/templates/layout.html:85
 #: project/templates/layout.html:100
 msgid "EventStatus.movedOnline"
 msgstr "Moved online"
 
-#: project/forms/event.py:348 project/templates/layout.html:88
+#: project/forms/event.py:368 project/templates/layout.html:88
 #: project/templates/layout.html:103
 msgid "EventStatus.postponed"
 msgstr "Postponed"
 
-#: project/forms/event.py:349 project/templates/layout.html:91
+#: project/forms/event.py:369 project/templates/layout.html:91
 #: project/templates/layout.html:106
 msgid "EventStatus.rescheduled"
 msgstr "Rescheduled"
 
-#: project/forms/event.py:351
+#: project/forms/event.py:371
 msgid "Select the status of the event."
 msgstr ""
 
-#: project/forms/event.py:355
+#: project/forms/event.py:375
 msgid "Public status"
 msgstr ""
 
-#: project/forms/event.py:358
+#: project/forms/event.py:378
 msgid "PublicStatus.published"
 msgstr ""
 
-#: project/forms/event.py:359 project/templates/_macros.html:282
+#: project/forms/event.py:379 project/templates/_macros.html:282
 msgid "PublicStatus.draft"
 msgstr ""
 
-#: project/forms/event.py:361
+#: project/forms/event.py:381
 msgid "Select the public status of the event."
 msgstr ""
 
-#: project/forms/event.py:364 project/templates/event/update.html:5
-#: project/templates/event/update.html:119
+#: project/forms/event.py:384 project/templates/event/update.html:5
+#: project/templates/event/update.html:141
 msgid "Update event"
 msgstr ""
 
-#: project/forms/event.py:378 project/templates/_macros.html:1218
+#: project/forms/event.py:398 project/templates/_macros.html:1234
 #: project/templates/event/actions.html:47
 #: project/templates/event/delete.html:6
 msgid "Delete event"
 msgstr ""
 
-#: project/forms/event.py:386 project/forms/event_date.py:15
+#: project/forms/event.py:406 project/forms/event_date.py:15
 #: project/forms/planing.py:14
 msgid "From"
 msgstr ""
 
-#: project/forms/event.py:388 project/forms/event_date.py:17
+#: project/forms/event.py:408 project/forms/event_date.py:17
 #: project/forms/planing.py:16
 msgid "to"
 msgstr ""
 
-#: project/forms/event.py:390 project/forms/event_date.py:19
+#: project/forms/event.py:410 project/forms/event_date.py:19
 msgid "Keyword"
 msgstr ""
 
-#: project/forms/event.py:392 project/forms/event_date.py:21
+#: project/forms/event.py:412 project/forms/event_date.py:21
 #: project/forms/planing.py:19 project/templates/_macros.html:392
 msgid "Category"
 msgstr ""
 
-#: project/forms/event.py:398
+#: project/forms/event.py:418
 msgid "Find events"
 msgstr ""
 
@@ -896,13 +910,13 @@ msgstr ""
 msgid "I would like to be notified by email after the review"
 msgstr ""
 
-#: project/forms/event_suggestion.py:52 project/templates/event/create.html:296
+#: project/forms/event_suggestion.py:52 project/templates/event/create.html:320
 msgid ""
 "Choose where the event takes place. If the venue is not yet in the list, "
 "just enter it."
 msgstr ""
 
-#: project/forms/event_suggestion.py:62 project/templates/event/create.html:266
+#: project/forms/event_suggestion.py:62 project/templates/event/create.html:288
 msgid ""
 "Select the organizer. If the organizer is not yet on the list, just enter"
 " it."
@@ -984,7 +998,7 @@ msgid "Weekdays"
 msgstr ""
 
 #: project/forms/reference.py:11 project/forms/reference_request.py:16
-#: project/templates/_macros.html:518 project/templates/_macros.html:675
+#: project/templates/_macros.html:512 project/templates/_macros.html:672
 #: project/templates/admin_unit/create.html:28
 #: project/templates/admin_unit/update.html:29
 #: project/templates/layout.html:258
@@ -1012,7 +1026,7 @@ msgstr ""
 msgid "Delete request"
 msgstr ""
 
-#: project/forms/reference_request.py:28 project/templates/_macros.html:1401
+#: project/forms/reference_request.py:28 project/templates/_macros.html:1417
 #: project/templates/event_suggestion/review_status.html:18
 #: project/templates/reference_request/review_status.html:12
 msgid "Review status"
@@ -1079,7 +1093,7 @@ msgid "This field is required."
 msgstr ""
 
 #: project/templates/_macros.html:134 project/templates/_macros.html:414
-#: project/templates/_macros.html:914
+#: project/templates/_macros.html:930
 msgid "Date"
 msgstr ""
 
@@ -1119,64 +1133,64 @@ msgstr ""
 msgid "Last updated at %(updated_at)s."
 msgstr ""
 
-#: project/templates/_macros.html:408 project/templates/_macros.html:571
+#: project/templates/_macros.html:408 project/templates/_macros.html:578
 #: project/templates/event/actions.html:12
-#: project/templates/event/create.html:235
+#: project/templates/event/create.html:257
 #: project/templates/event/delete.html:13
-#: project/templates/event/update.html:126
+#: project/templates/event/update.html:148
 #: project/templates/widget/event_suggestion/create.html:229
 msgid "Event"
 msgstr ""
 
-#: project/templates/_macros.html:441 project/templates/_macros.html:593
-#: project/templates/_macros.html:1470 project/templates/event/actions.html:32
+#: project/templates/_macros.html:441 project/templates/_macros.html:600
+#: project/templates/_macros.html:1486 project/templates/event/actions.html:32
 msgid "Share"
 msgstr ""
 
-#: project/templates/_macros.html:445 project/templates/_macros.html:597
-#: project/templates/_macros.html:1500
+#: project/templates/_macros.html:445 project/templates/_macros.html:604
+#: project/templates/_macros.html:1516
 msgid "Add to calendar"
 msgstr ""
 
-#: project/templates/_macros.html:453 project/templates/_macros.html:605
+#: project/templates/_macros.html:453 project/templates/_macros.html:612
 #: project/templates/event/report.html:4
 msgid "Report event"
 msgstr ""
 
-#: project/templates/_macros.html:480 project/templates/_macros.html:631
+#: project/templates/_macros.html:480 project/templates/_macros.html:638
 msgid "Show directions"
 msgstr ""
 
-#: project/templates/_macros.html:485 project/templates/_macros.html:636
+#: project/templates/_macros.html:485 project/templates/_macros.html:643
 msgid "The event takes place online."
 msgstr ""
 
-#: project/templates/_macros.html:487 project/templates/_macros.html:638
+#: project/templates/_macros.html:487 project/templates/_macros.html:645
 msgid "The event takes place both offline and online."
 msgstr ""
 
-#: project/templates/_macros.html:699 project/templates/event_date/list.html:5
+#: project/templates/_macros.html:696 project/templates/event_date/list.html:5
 #: project/templates/event_date/list.html:300
 #: project/templates/event_date/search.html:3
 #: project/templates/reference_request/review.html:32
 msgid "Event Dates"
 msgstr ""
 
-#: project/templates/_macros.html:772
+#: project/templates/_macros.html:788
 msgid "Search location on Google"
 msgstr ""
 
-#: project/templates/_macros.html:838
+#: project/templates/_macros.html:854
 #, python-format
 msgid "%(count)d event dates"
 msgstr ""
 
-#: project/templates/_macros.html:854 project/templates/_macros.html:856
+#: project/templates/_macros.html:870 project/templates/_macros.html:872
 #: project/templates/event_date/list.html:321
 msgid "First"
 msgstr ""
 
-#: project/templates/_macros.html:859 project/templates/_macros.html:861
+#: project/templates/_macros.html:875 project/templates/_macros.html:877
 #: project/templates/event_date/list.html:322
 #: project/templates/widget/event_suggestion/create.html:193
 #: project/templates/widget/event_suggestion/create.html:218
@@ -1187,12 +1201,12 @@ msgstr ""
 msgid "Previous"
 msgstr ""
 
-#: project/templates/_macros.html:863
+#: project/templates/_macros.html:879
 #, python-format
 msgid "Page %(page)d of %(pages)d (%(total)d total)"
 msgstr ""
 
-#: project/templates/_macros.html:865 project/templates/_macros.html:867
+#: project/templates/_macros.html:881 project/templates/_macros.html:883
 #: project/templates/event_date/list.html:324
 #: project/templates/widget/event_suggestion/create.html:194
 #: project/templates/widget/event_suggestion/create.html:219
@@ -1202,73 +1216,73 @@ msgstr ""
 msgid "Next"
 msgstr ""
 
-#: project/templates/_macros.html:870 project/templates/_macros.html:872
+#: project/templates/_macros.html:886 project/templates/_macros.html:888
 #: project/templates/event_date/list.html:325
 msgid "Last"
 msgstr ""
 
-#: project/templates/_macros.html:937
+#: project/templates/_macros.html:953
 msgid "Radius"
 msgstr ""
 
-#: project/templates/_macros.html:1147
+#: project/templates/_macros.html:1163
 msgid "Edit image"
 msgstr ""
 
-#: project/templates/_macros.html:1168
+#: project/templates/_macros.html:1184
 msgid "Close"
 msgstr ""
 
-#: project/templates/_macros.html:1169
+#: project/templates/_macros.html:1185
 msgid "Okay"
 msgstr ""
 
-#: project/templates/_macros.html:1181
+#: project/templates/_macros.html:1197
 msgid "Choose image file"
 msgstr ""
 
-#: project/templates/_macros.html:1217 project/templates/event/actions.html:46
+#: project/templates/_macros.html:1233 project/templates/event/actions.html:46
 msgid "Edit event"
 msgstr ""
 
-#: project/templates/_macros.html:1220 project/templates/manage/events.html:40
+#: project/templates/_macros.html:1236 project/templates/manage/events.html:40
 msgid "More"
 msgstr ""
 
-#: project/templates/_macros.html:1267
+#: project/templates/_macros.html:1283
 msgid "Please enter a valid time, between 00:00 and 23:59."
 msgstr ""
 
-#: project/templates/_macros.html:1295
+#: project/templates/_macros.html:1311
 #, python-format
 msgid "Just use %(term)s"
 msgstr ""
 
-#: project/templates/_macros.html:1361
+#: project/templates/_macros.html:1377
 msgid "Event suggestion"
 msgstr ""
 
-#: project/templates/_macros.html:1479
+#: project/templates/_macros.html:1495
 msgid "Link copied"
 msgstr ""
 
-#: project/templates/_macros.html:1479
+#: project/templates/_macros.html:1495
 msgid "Copy link"
 msgstr ""
 
-#: project/templates/_macros.html:1508
+#: project/templates/_macros.html:1524
 msgid "Google calendar"
 msgstr ""
 
-#: project/templates/_macros.html:1509
+#: project/templates/_macros.html:1525
 msgid "Apple calendar"
 msgstr ""
 
-#: project/templates/_macros.html:1510
+#: project/templates/_macros.html:1526
 msgid "Yahoo calendar"
 msgstr ""
 
-#: project/templates/_macros.html:1511
+#: project/templates/_macros.html:1527
 msgid "Other calendar"
 msgstr ""
 
@@ -1328,7 +1342,7 @@ msgid "Show events"
 msgstr ""
 
 #: project/templates/event/create.html:5
-#: project/templates/event/create.html:228 project/templates/layout.html:226
+#: project/templates/event/create.html:250 project/templates/layout.html:226
 #: project/templates/manage/events.html:22
 #: project/templates/manage/organizers.html:21
 msgid "Create event"
@@ -1445,8 +1459,8 @@ msgstr ""
 
 #: project/templates/admin_unit/create.html:58
 #: project/templates/admin_unit/update.html:59
-#: project/templates/event/create.html:354
-#: project/templates/event/update.html:211
+#: project/templates/event/create.html:378
+#: project/templates/event/update.html:234
 #: project/templates/event_place/create.html:57
 #: project/templates/event_place/update.html:57
 #: project/templates/organizer/create.html:56
@@ -1571,31 +1585,33 @@ msgid "Enter place or address"
 msgstr ""
 
 #: project/templates/event/create.html:183
+#: project/templates/event/create.html:240
 #: project/templates/event/update.html:106
+#: project/templates/event/update.html:132
 #: project/templates/widget/event_suggestion/create.html:129
 msgid "Enter organizer"
 msgstr ""
 
-#: project/templates/event/create.html:245
-#: project/templates/event/update.html:136
+#: project/templates/event/create.html:267
+#: project/templates/event/update.html:158
 msgid "Event date"
 msgstr ""
 
-#: project/templates/event/create.html:283
+#: project/templates/event/create.html:305
 msgid "Switch to organizer search"
 msgstr ""
 
-#: project/templates/event/create.html:316
+#: project/templates/event/create.html:340
 msgid "Switch to place search"
 msgstr ""
 
-#: project/templates/event/create.html:327
-#: project/templates/event/update.html:184
+#: project/templates/event/create.html:351
+#: project/templates/event/update.html:207
 msgid "Access"
 msgstr ""
 
-#: project/templates/event/create.html:341
-#: project/templates/event/update.html:198
+#: project/templates/event/create.html:365
+#: project/templates/event/update.html:221
 msgid "Target group"
 msgstr ""
 
@@ -1901,11 +1917,11 @@ msgstr ""
 msgid "Event successfully deleted"
 msgstr ""
 
-#: project/views/event.py:397
+#: project/views/event.py:404
 msgid "Referenced event changed"
 msgstr ""
 
-#: project/views/event.py:420
+#: project/views/event.py:427
 msgid "New event report"
 msgstr ""
 
diff --git a/project/views/event.py b/project/views/event.py
index 21e7976..86109ae 100644
--- a/project/views/event.py
+++ b/project/views/event.py
@@ -300,9 +300,16 @@ def prepare_organizer(form):
         if organizer:
             form.organizer_id.choices = [(organizer.id, organizer.name)]
 
+    if form.co_organizer_ids.data and len(form.co_organizer_ids.data) > 0:
+        co_organizers = EventOrganizer.query.filter(
+            EventOrganizer.id.in_(form.co_organizer_ids.data)
+        ).all()
+        form.co_organizer_ids.choices = [(o.id, o.name) for o in co_organizers]
+
 
 def prepare_event_form(form):
     form.category_ids.choices = get_event_category_choices()
+    form.co_organizer_ids.choices = list()
 
     prepare_organizer(form)
     prepare_event_place(form)
diff --git a/project/views/utils.py b/project/views/utils.py
index 9d530e8..ab3ff33 100644
--- a/project/views/utils.py
+++ b/project/views/utils.py
@@ -48,7 +48,7 @@ def handleSqlError(e: SQLAlchemyError) -> str:
         return str(e)
 
     prefix = None
-    message = str(e.orig)
+    message = gettext(e.orig.message) if hasattr(e.orig, "message") else str(e.orig)
 
     if e.orig.pgcode == UNIQUE_VIOLATION:
         prefix = gettext(
diff --git a/tests/api/test_event.py b/tests/api/test_event.py
index 1afb1c7..cbb5254 100644
--- a/tests/api/test_event.py
+++ b/tests/api/test_event.py
@@ -41,6 +41,19 @@ def test_read_myDraft(client, app, db, seeder, utils):
     assert response.json["public_status"] == "draft"
 
 
+def test_read_co_organizers(client, app, db, seeder, utils):
+    user_id, admin_unit_id = seeder.setup_base()
+    event_id, organizer_a_id, organizer_b_id = seeder.create_event_with_co_organizers(
+        admin_unit_id
+    )
+
+    url = utils.get_url("api_v1_event", id=event_id)
+    response = utils.get_json(url)
+    utils.assert_response_ok(response)
+    assert response.json["co_organizers"][0]["id"] == organizer_a_id
+    assert response.json["co_organizers"][1]["id"] == organizer_b_id
+
+
 def test_list(client, seeder, utils):
     user_id, admin_unit_id = seeder.setup_base()
     event_id = seeder.create_event(admin_unit_id)
@@ -251,6 +264,53 @@ def test_put_organizerFromAnotherAdminUnit(client, seeder, utils, app):
     utils.assert_response_api_error(response, "Check Violation")
 
 
+def test_put_co_organizers(client, seeder, utils, app):
+    user_id, admin_unit_id = seeder.setup_api_access()
+    event_id = seeder.create_event(admin_unit_id)
+    place_id = seeder.upsert_default_event_place(admin_unit_id)
+    organizer_id = seeder.upsert_default_event_organizer(admin_unit_id)
+    organizer_a_id = seeder.upsert_event_organizer(admin_unit_id, "Organizer A")
+    organizer_b_id = seeder.upsert_event_organizer(admin_unit_id, "Organizer B")
+
+    put = create_put(place_id, organizer_id)
+    put["co_organizers"] = [
+        {"id": organizer_a_id},
+        {"id": organizer_b_id},
+    ]
+
+    url = utils.get_url("api_v1_event", id=event_id)
+    response = utils.put_json(url, put)
+    utils.assert_response_no_content(response)
+
+    with app.app_context():
+        from project.models import Event
+
+        event = Event.query.get(event_id)
+        assert len(event.co_organizers) == 2
+        assert event.co_organizers[0].id == organizer_a_id
+        assert event.co_organizers[1].id == organizer_b_id
+
+
+def test_put_co_organizerFromAnotherAdminUnit(client, seeder, utils, app):
+    user_id, admin_unit_id = seeder.setup_api_access()
+    event_id = seeder.create_event(admin_unit_id)
+    place_id = seeder.upsert_default_event_place(admin_unit_id)
+    organizer_id = seeder.upsert_default_event_organizer(admin_unit_id)
+
+    other_admin_unit_id = seeder.create_admin_unit(user_id, "Other Crew")
+    organizer_a_id = seeder.upsert_event_organizer(other_admin_unit_id, "Organizer A")
+
+    put = create_put(place_id, organizer_id)
+    put["co_organizers"] = [
+        {"id": organizer_a_id},
+    ]
+
+    url = utils.get_url("api_v1_event", id=event_id)
+    response = utils.put_json(url, put)
+    utils.assert_response_bad_request(response)
+    utils.assert_response_api_error(response, "Check Violation")
+
+
 def test_put_invalidDateFormat(client, seeder, utils, app):
     user_id, admin_unit_id = seeder.setup_api_access()
     event_id = seeder.create_event(admin_unit_id)
diff --git a/tests/api/test_organization.py b/tests/api/test_organization.py
index 453054b..a1452a5 100644
--- a/tests/api/test_organization.py
+++ b/tests/api/test_organization.py
@@ -48,7 +48,10 @@ def test_event_search(client, seeder, utils):
     response = utils.get_json(url)
     utils.assert_response_ok(response)
     assert len(response.json["items"]) == 2
-    assert response.json["items"][1]["public_status"] == "draft"
+    assert (
+        response.json["items"][0]["public_status"] == "draft"
+        or response.json["items"][1]["public_status"] == "draft"
+    )
 
 
 def test_organizers(client, seeder, utils):
@@ -142,6 +145,30 @@ def test_events_post(client, seeder, utils, app, allday):
         assert event.allday == allday
 
 
+def test_events_post_co_organizers(client, seeder, utils, app):
+    url, data, admin_unit_id, place_id, organizer_id = prepare_events_post_data(
+        seeder, utils
+    )
+    organizer_a_id = seeder.upsert_event_organizer(admin_unit_id, "Organizer A")
+    organizer_b_id = seeder.upsert_event_organizer(admin_unit_id, "Organizer B")
+
+    data["co_organizers"] = [
+        {"id": organizer_a_id},
+        {"id": organizer_b_id},
+    ]
+    response = utils.post_json(url, data)
+    utils.assert_response_created(response)
+    event_id = int(response.json["id"])
+
+    with app.app_context():
+        from project.models import Event
+
+        event = Event.query.get(event_id)
+        assert len(event.co_organizers) == 2
+        assert event.co_organizers[0].id == organizer_a_id
+        assert event.co_organizers[1].id == organizer_b_id
+
+
 def test_events_post_photo_no_data(client, seeder, utils, app):
     url, data, admin_unit_id, place_id, organizer_id = prepare_events_post_data(
         seeder, utils
diff --git a/tests/cli/test_dump.py b/tests/cli/test_dump.py
index e4a71e1..22c48fc 100644
--- a/tests/cli/test_dump.py
+++ b/tests/cli/test_dump.py
@@ -1,6 +1,7 @@
 def test_all(client, seeder, app, utils):
     user_id, admin_unit_id = seeder.setup_base()
     seeder.create_event(admin_unit_id, "RRULE:FREQ=DAILY;COUNT=7")
+    seeder.create_event_with_co_organizers(admin_unit_id)
 
     runner = app.test_cli_runner()
     result = runner.invoke(args=["dump", "all"])
diff --git a/tests/conftest.py b/tests/conftest.py
index ab191d7..24c1d09 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -33,12 +33,15 @@ def app():
 
 @pytest.fixture
 def db(app):
+    from flask_migrate import stamp
+
     from project import db
     from project.init_data import create_initial_data
 
     with app.app_context():
         db.drop_all()
         db.create_all()
+        stamp()
         create_initial_data()
 
     return db
diff --git a/tests/form.py b/tests/form.py
index 72208c3..7309ebd 100644
--- a/tests/form.py
+++ b/tests/form.py
@@ -115,7 +115,7 @@ class Form:
         # Override any form values with our input
         for key, value in values.items():
             if key in filled:
-                filled.pop(key)
+                del filled[key]
             if type(value) is list:
                 filled.setlist(key, value)
             else:
diff --git a/tests/seeder.py b/tests/seeder.py
index bac0b88..88b77c4 100644
--- a/tests/seeder.py
+++ b/tests/seeder.py
@@ -199,8 +199,14 @@ class Seeder(object):
         name="Name",
         start=None,
         allday=False,
+        co_organizer_ids=None,
     ):
-        from project.models import Event, EventAttendanceMode, PublicStatus
+        from project.models import (
+            Event,
+            EventAttendanceMode,
+            EventOrganizer,
+            PublicStatus,
+        )
         from project.services.event import insert_event, upsert_event_category
 
         with self._app.app_context():
@@ -224,11 +230,25 @@ class Seeder(object):
             if draft:
                 event.public_status = PublicStatus.draft
 
+            if co_organizer_ids:
+                co_organizers = EventOrganizer.query.filter(
+                    EventOrganizer.id.in_(co_organizer_ids)
+                ).all()
+                event.co_organizers = co_organizers
+
             insert_event(event)
             self._db.session.commit()
             event_id = event.id
         return event_id
 
+    def create_event_with_co_organizers(self, admin_unit_id):
+        organizer_a_id = self.upsert_event_organizer(admin_unit_id, "Organizer A")
+        organizer_b_id = self.upsert_event_organizer(admin_unit_id, "Organizer B")
+        event_id = self.create_event(
+            admin_unit_id, co_organizer_ids=[organizer_a_id, organizer_b_id]
+        )
+        return (event_id, organizer_a_id, organizer_b_id)
+
     def create_event_via_form(self, admin_unit_id: int) -> str:
         place_id = self.upsert_default_event_place(admin_unit_id)
         organizer_id = self.upsert_default_event_organizer(admin_unit_id)
diff --git a/tests/test_jsonld.py b/tests/test_jsonld.py
index e2c8607..2ce6372 100644
--- a/tests/test_jsonld.py
+++ b/tests/test_jsonld.py
@@ -166,6 +166,25 @@ def test_get_sd_for_event_date_allday(client, app, db, seeder, utils):
         assert '"endDate": "2030-12-31"' in structured_data
 
 
+def test_get_sd_for_event_date_with_co_organizer(client, app, db, seeder, utils):
+    user_id, admin_unit_id = seeder.setup_base()
+    event_id, organizer_a_id, organizer_b_id = seeder.create_event_with_co_organizers(
+        admin_unit_id
+    )
+
+    with app.app_context():
+        from project.jsonld import get_sd_for_event_date
+        from project.models import Event
+
+        event = Event.query.get(event_id)
+        event_date = event.dates[0]
+
+        with app.test_request_context():
+            data = get_sd_for_event_date(event_date)
+
+        assert len(data["organizer"]) == 4
+
+
 @pytest.mark.parametrize(
     "age_from, age_to, typicalAgeRange",
     [(18, None, "18-"), (None, 14, "-14"), (9, 99, "9-99")],
diff --git a/tests/test_models.py b/tests/test_models.py
index 1157164..347de48 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -158,3 +158,28 @@ def test_admin_unit_deletion(client, app, db, seeder):
 
         assert AdminUnit.query.get(other_admin_unit_id) is not None
         assert Event.query.get(other_event_id) is not None
+
+
+def test_event_co_organizers_deletion(client, app, db, seeder):
+    user_id, admin_unit_id = seeder.setup_base(log_in=False)
+    event_id, organizer_a_id, organizer_b_id = seeder.create_event_with_co_organizers(
+        admin_unit_id
+    )
+
+    with app.app_context():
+        from project.models import Event, EventOrganizer
+
+        event = Event.query.get(event_id)
+        assert len(event.co_organizers) == 2
+        assert event.co_organizers[0].id == organizer_a_id
+        assert event.co_organizers[1].id == organizer_b_id
+
+        organizer_a = EventOrganizer.query.get(organizer_a_id)
+        db.session.delete(organizer_a)
+        db.session.commit()
+        assert len(event.co_organizers) == 1
+        assert event.co_organizers[0].id == organizer_b_id
+
+        db.session.delete(event)
+        db.session.commit()
+        assert EventOrganizer.query.get(organizer_b_id).id is not None
diff --git a/tests/views/test_event.py b/tests/views/test_event.py
index 37012c9..f098517 100644
--- a/tests/views/test_event.py
+++ b/tests/views/test_event.py
@@ -34,6 +34,18 @@ def test_read_containsActionLink(seeder, utils):
     assert action_url in str(response.data)
 
 
+def test_read_co_organizers(seeder, utils):
+    user_id, admin_unit_id = seeder.setup_base()
+    event_id, organizer_a_id, organizer_b_id = seeder.create_event_with_co_organizers(
+        admin_unit_id
+    )
+
+    url = utils.get_url("event", event_id=event_id)
+    response = utils.get_ok(url)
+    utils.assert_response_contains(response, "Organizer A")
+    utils.assert_response_contains(response, "Organizer B")
+
+
 @pytest.mark.parametrize("db_error", [True, False])
 def test_create(client, app, utils, seeder, mocker, db_error):
     user_id, admin_unit_id = seeder.setup_base()
@@ -182,6 +194,27 @@ def test_create_missingPlace(client, app, utils, seeder, mocker):
 def test_create_missingOrganizer(client, app, utils, seeder, mocker):
     user_id, admin_unit_id = seeder.setup_base()
     place_id = seeder.upsert_default_event_place(admin_unit_id)
+
+    url = utils.get_url("event_create_for_admin_unit_id", id=admin_unit_id)
+    response = utils.get_ok(url)
+
+    response = utils.post_form(
+        url,
+        response,
+        {
+            "name": "Name",
+            "description": "Beschreibung",
+            "start": ["2030-12-31", "23:59"],
+            "event_place_id": place_id,
+        },
+    )
+
+    utils.assert_response_error_message(response)
+
+
+def test_create_invalidOrganizer(client, app, utils, seeder, mocker):
+    user_id, admin_unit_id = seeder.setup_base()
+    place_id = seeder.upsert_default_event_place(admin_unit_id)
     organizer_id = seeder.upsert_default_event_organizer(admin_unit_id)
 
     url = utils.get_url("event_create_for_admin_unit_id", id=admin_unit_id)
@@ -193,13 +226,15 @@ def test_create_missingOrganizer(client, app, utils, seeder, mocker):
         {
             "name": "Name",
             "description": "Beschreibung",
-            "start": ["31.12.2030", "23:59"],
+            "start": ["2030-12-31", "23:59"],
             "event_place_id": place_id,
             "organizer_id": organizer_id,
+            "co_organizer_ids": [organizer_id],
         },
     )
 
     utils.assert_response_error_message(response)
+    utils.assert_response_contains(response, "Ungültiger Mitveranstalter")
 
 
 def test_create_invalidDateFormat(client, app, utils, seeder, mocker):
@@ -223,6 +258,27 @@ def test_create_invalidDateFormat(client, app, utils, seeder, mocker):
     utils.assert_response_error_message(response)
 
 
+def test_create_startInvalid(client, app, utils, seeder, mocker):
+    user_id, admin_unit_id = seeder.setup_base()
+    place_id = seeder.upsert_default_event_place(admin_unit_id)
+
+    url = utils.get_url("event_create_for_admin_unit_id", id=admin_unit_id)
+    response = utils.get_ok(url)
+
+    response = utils.post_form(
+        url,
+        response,
+        {
+            "name": "Name",
+            "start": ["31.12.2030", "23:59"],
+            "end": ["2030-12-31", "23:58"],
+            "event_place_id": place_id,
+        },
+    )
+
+    utils.assert_response_error_message(response)
+
+
 def test_create_startAfterEnd(client, app, utils, seeder, mocker):
     user_id, admin_unit_id = seeder.setup_base()
     place_id = seeder.upsert_default_event_place(admin_unit_id)
@@ -445,6 +501,28 @@ def test_update(client, seeder, utils, app, mocker, db_error):
         assert event is not None
 
 
+def test_update_co_organizers(client, seeder, utils, app):
+    user_id, admin_unit_id = seeder.setup_base()
+    event_id, organizer_a_id, organizer_b_id = seeder.create_event_with_co_organizers(
+        admin_unit_id
+    )
+
+    url = utils.get_url("event_update", event_id=event_id)
+    response = utils.get_ok(url)
+
+    response = utils.post_form(
+        url,
+        response,
+        {
+            "name": "Neuer Name",
+        },
+    )
+
+    utils.assert_response_redirect(
+        response, "manage_admin_unit_events", id=admin_unit_id
+    )
+
+
 @pytest.mark.parametrize("db_error", [True, False])
 def test_delete(client, seeder, utils, app, mocker, db_error):
     user_id, admin_unit_id = seeder.setup_base()
diff --git a/tests/views/test_widget.py b/tests/views/test_widget.py
index 17f7eb7..ef5bc0d 100644
--- a/tests/views/test_widget.py
+++ b/tests/views/test_widget.py
@@ -90,6 +90,20 @@ def test_event_date(client, seeder, utils, app, db):
     utils.assert_response_unauthorized(response)
 
 
+def test_event_date_co_organizers(client, seeder, utils, app, db):
+    user_id, admin_unit_id = seeder.setup_base(log_in=False)
+    event_id, organizer_a_id, organizer_b_id = seeder.create_event_with_co_organizers(
+        admin_unit_id
+    )
+    au_short_name = "meinecrew"
+
+    url = utils.get_url("widget_event_date", au_short_name=au_short_name, id=event_id)
+    response = utils.get(url)
+    response = utils.get_ok(url)
+    utils.assert_response_contains(response, "Organizer A")
+    utils.assert_response_contains(response, "Organizer B")
+
+
 def get_create_data():
     return {
         "accept_tos": "y",