diff --git a/src/Infrastructure.Dapper/AdminConsole/Helpers/BulkResourceCreationService.cs b/src/Infrastructure.Dapper/AdminConsole/Helpers/BulkResourceCreationService.cs
index 2be33e8846..a063ec25b1 100644
--- a/src/Infrastructure.Dapper/AdminConsole/Helpers/BulkResourceCreationService.cs
+++ b/src/Infrastructure.Dapper/AdminConsole/Helpers/BulkResourceCreationService.cs
@@ -156,6 +156,8 @@ public static class BulkResourceCreationService
         collectionsTable.Columns.Add(typeColumn);
         var defaultUserCollectionEmailColumn = new DataColumn(nameof(collection.DefaultUserCollectionEmail), typeof(string));
         collectionsTable.Columns.Add(defaultUserCollectionEmailColumn);
+        var defaultCollectionOwnerIdColumn = new DataColumn(nameof(collection.DefaultCollectionOwnerId), typeof(Guid));
+        collectionsTable.Columns.Add(defaultCollectionOwnerIdColumn);
 
         foreach (DataColumn col in collectionsTable.Columns)
         {
@@ -178,6 +180,7 @@ public static class BulkResourceCreationService
             row[externalIdColumn] = collectionRecord.ExternalId;
             row[typeColumn] = collectionRecord.Type;
             row[defaultUserCollectionEmailColumn] = collectionRecord.DefaultUserCollectionEmail;
+            row[defaultCollectionOwnerIdColumn] = collectionRecord.DefaultCollectionOwnerId;
 
             collectionsTable.Rows.Add(row);
         }
diff --git a/src/Infrastructure.EntityFramework/AdminConsole/Repositories/OrganizationRepository.cs b/src/Infrastructure.EntityFramework/AdminConsole/Repositories/OrganizationRepository.cs
index f2da58a1dd..894c3ed620 100644
--- a/src/Infrastructure.EntityFramework/AdminConsole/Repositories/OrganizationRepository.cs
+++ b/src/Infrastructure.EntityFramework/AdminConsole/Repositories/OrganizationRepository.cs
@@ -10,6 +10,7 @@ using Bit.Core.Enums;
 using Bit.Core.Models.Data.Organizations;
 using Bit.Core.Models.Data.Organizations.OrganizationUsers;
 using Bit.Core.Repositories;
+using Bit.Infrastructure.EntityFramework.Models;
 using LinqToDB.Tools;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.DependencyInjection;
@@ -190,6 +191,8 @@ public class OrganizationRepository : Repository<Core.AdminConsole.Entities.Orga
             await deleteCiphersTransaction.CommitAsync();
 
             var organizationDeleteTransaction = await dbContext.Database.BeginTransactionAsync();
+            await dbContext.Collections.Where(c => c.OrganizationId == organization.Id)
+                .ExecuteDeleteAsync();
             await dbContext.AuthRequests.Where(ar => ar.OrganizationId == organization.Id)
                 .ExecuteDeleteAsync();
             await dbContext.SsoUsers.Where(su => su.OrganizationId == organization.Id)
diff --git a/src/Infrastructure.EntityFramework/AdminConsole/Repositories/OrganizationUserRepository.cs b/src/Infrastructure.EntityFramework/AdminConsole/Repositories/OrganizationUserRepository.cs
index 0edd5e9ccd..087a5927d0 100644
--- a/src/Infrastructure.EntityFramework/AdminConsole/Repositories/OrganizationUserRepository.cs
+++ b/src/Infrastructure.EntityFramework/AdminConsole/Repositories/OrganizationUserRepository.cs
@@ -218,6 +218,7 @@ public class OrganizationUserRepository : Repository<Core.Entities.OrganizationU
                             }
                         }
                         collection.Type = CollectionType.SharedCollection;
+                        collection.DefaultCollectionOwnerId = null;
                     }
                 }
             }
diff --git a/src/Sql/dbo/Stored Procedures/Organization_DeleteById.sql b/src/Sql/dbo/Stored Procedures/Organization_DeleteById.sql
index 50ad247c1a..1618831df3 100644
--- a/src/Sql/dbo/Stored Procedures/Organization_DeleteById.sql	
+++ b/src/Sql/dbo/Stored Procedures/Organization_DeleteById.sql	
@@ -44,6 +44,12 @@ BEGIN
     WHERE
         [OrganizationId] = @Id
 
+    DELETE C
+    FROM
+        [dbo].[Collection] C
+    WHERE
+        [OrganizationId] = @Id
+
     DELETE CU
     FROM
         [dbo].[CollectionUser] CU
diff --git a/util/Migrator/DbScripts/2025-12-20_00_Collection_AddDefaultCollectionOwnerAndConstraint.sql b/util/Migrator/DbScripts/2025-12-20_00_Collection_AddDefaultCollectionOwnerAndConstraint.sql
index 19150cc9c3..488abfbe65 100644
--- a/util/Migrator/DbScripts/2025-12-20_00_Collection_AddDefaultCollectionOwnerAndConstraint.sql
+++ b/util/Migrator/DbScripts/2025-12-20_00_Collection_AddDefaultCollectionOwnerAndConstraint.sql
@@ -134,3 +134,175 @@ BEGIN
     EXECUTE sp_refreshsqlmodule N'[dbo].[UserCollectionDetails]';
 END
 GO
+
+-- TODO: better place for this?
+-- Update Organization_Delete to null out this column
+-- Can't be cascaded due to competing cascades
+CREATE OR ALTER PROCEDURE [dbo].[Organization_DeleteById]
+@Id UNIQUEIDENTIFIER
+    WITH RECOMPILE
+AS
+BEGIN
+    SET NOCOUNT ON
+
+    EXEC [dbo].[User_BumpAccountRevisionDateByOrganizationId] @Id
+
+    DECLARE @BatchSize INT = 100
+    WHILE @BatchSize > 0
+        BEGIN
+            BEGIN TRANSACTION Organization_DeleteById_Ciphers
+
+                DELETE TOP(@BatchSize)
+                FROM
+                    [dbo].[Cipher]
+                WHERE
+                    [UserId] IS NULL
+                  AND [OrganizationId] = @Id
+
+                SET @BatchSize = @@ROWCOUNT
+
+            COMMIT TRANSACTION Organization_DeleteById_Ciphers
+        END
+
+    BEGIN TRANSACTION Organization_DeleteById
+
+        DELETE
+        FROM
+            [dbo].[AuthRequest]
+        WHERE
+            [OrganizationId] = @Id
+
+        DELETE
+        FROM
+            [dbo].[SsoUser]
+        WHERE
+            [OrganizationId] = @Id
+
+        DELETE
+        FROM
+            [dbo].[SsoConfig]
+        WHERE
+            [OrganizationId] = @Id
+
+        DELETE C
+        FROM
+            [dbo].[Collection] C
+        WHERE
+            [OrganizationId] = @Id
+
+        DELETE CU
+        FROM
+            [dbo].[CollectionUser] CU
+                INNER JOIN
+            [dbo].[OrganizationUser] OU ON [CU].[OrganizationUserId] = [OU].[Id]
+        WHERE
+            [OU].[OrganizationId] = @Id
+
+        DELETE AP
+        FROM
+            [dbo].[AccessPolicy] AP
+                INNER JOIN
+            [dbo].[OrganizationUser] OU ON [AP].[OrganizationUserId] = [OU].[Id]
+        WHERE
+            [OU].[OrganizationId] = @Id
+
+        DELETE GU
+        FROM
+            [dbo].[GroupUser] GU
+                INNER JOIN
+            [dbo].[OrganizationUser] OU ON [GU].[OrganizationUserId] = [OU].[Id]
+        WHERE
+            [OU].[OrganizationId] = @Id
+
+        DELETE
+        FROM
+            [dbo].[OrganizationUser]
+        WHERE
+            [OrganizationId] = @Id
+
+        DELETE
+        FROM
+            [dbo].[ProviderOrganization]
+        WHERE
+            [OrganizationId] = @Id
+
+        EXEC [dbo].[OrganizationApiKey_OrganizationDeleted] @Id
+        EXEC [dbo].[OrganizationConnection_OrganizationDeleted] @Id
+        EXEC [dbo].[OrganizationSponsorship_OrganizationDeleted] @Id
+        EXEC [dbo].[OrganizationDomain_OrganizationDeleted] @Id
+        EXEC [dbo].[OrganizationIntegration_OrganizationDeleted] @Id
+
+        DELETE
+        FROM
+            [dbo].[Project]
+        WHERE
+            [OrganizationId] = @Id
+
+        DELETE
+        FROM
+            [dbo].[Secret]
+        WHERE
+            [OrganizationId] = @Id
+
+        DELETE AK
+        FROM
+            [dbo].[ApiKey] AK
+                INNER JOIN
+            [dbo].[ServiceAccount] SA ON [AK].[ServiceAccountId] = [SA].[Id]
+        WHERE
+            [SA].[OrganizationId] = @Id
+
+        DELETE AP
+        FROM
+            [dbo].[AccessPolicy] AP
+                INNER JOIN
+            [dbo].[ServiceAccount] SA ON [AP].[GrantedServiceAccountId] = [SA].[Id]
+        WHERE
+            [SA].[OrganizationId] = @Id
+
+        DELETE
+        FROM
+            [dbo].[ServiceAccount]
+        WHERE
+            [OrganizationId] = @Id
+
+        -- Delete Notification Status
+        DELETE
+            NS
+        FROM
+            [dbo].[NotificationStatus] NS
+                INNER JOIN
+            [dbo].[Notification] N ON N.[Id] = NS.[NotificationId]
+        WHERE
+            N.[OrganizationId] = @Id
+
+        -- Delete Notification
+        DELETE
+        FROM
+            [dbo].[Notification]
+        WHERE
+            [OrganizationId] = @Id
+
+        -- Delete Organization Application
+        DELETE
+        FROM
+            [dbo].[OrganizationApplication]
+        WHERE
+            [OrganizationId] = @Id
+
+        -- Delete Organization Report
+        DELETE
+        FROM
+            [dbo].[OrganizationReport]
+        WHERE
+            [OrganizationId] = @Id
+
+        DELETE
+        FROM
+            [dbo].[Organization]
+        WHERE
+            [Id] = @Id
+
+    COMMIT TRANSACTION Organization_DeleteById
+END
+