diff --git a/django/db/backends/oracle/schema.py b/django/db/backends/oracle/schema.py
index 2d9c9699a0..3356788a82 100644
--- a/django/db/backends/oracle/schema.py
+++ b/django/db/backends/oracle/schema.py
@@ -23,7 +23,7 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
         if isinstance(value, (datetime.date, datetime.time, datetime.datetime)):
             return "'%s'" % value
         elif isinstance(value, str):
-            return "'%s'" % value.replace("\'", "\'\'")
+            return "'%s'" % value.replace("\'", "\'\'").replace('%', '%%')
         elif isinstance(value, (bytes, bytearray, memoryview)):
             return "'%s'" % value.hex()
         elif isinstance(value, bool):
diff --git a/django/db/backends/postgresql/schema.py b/django/db/backends/postgresql/schema.py
index 3319ee09a9..0738f009cd 100644
--- a/django/db/backends/postgresql/schema.py
+++ b/django/db/backends/postgresql/schema.py
@@ -24,6 +24,8 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
     sql_delete_procedure = 'DROP FUNCTION %(procedure)s(%(param_types)s)'
 
     def quote_value(self, value):
+        if isinstance(value, str):
+            value = value.replace('%', '%%')
         # getquoted() returns a quoted bytestring of the adapted value.
         return psycopg2.extensions.adapt(value).getquoted().decode()
 
diff --git a/docs/releases/2.2.1.txt b/docs/releases/2.2.1.txt
index 9f241b83e9..90c9a06e79 100644
--- a/docs/releases/2.2.1.txt
+++ b/docs/releases/2.2.1.txt
@@ -70,3 +70,7 @@ Bugfixes
 
 * Fixed a regression in Django 2.2 where changes were not reliably detected by
   auto-reloader when using ``StatReloader`` (:ticket:`30323`).
+
+* Fixed a migration crash on Oracle and PostgreSQL when adding a check
+  constraint with a ``contains``, ``startswith``, or ``endswith`` lookup (or
+  their case-insensitive variant) (:ticket:`30408`).
diff --git a/tests/migrations/test_operations.py b/tests/migrations/test_operations.py
index d5c8396596..520a2b2204 100644
--- a/tests/migrations/test_operations.py
+++ b/tests/migrations/test_operations.py
@@ -1855,6 +1855,49 @@ class OperationTests(OperationTestBase):
         self.assertEqual(definition[1], [])
         self.assertEqual(definition[2], {'model_name': "Pony", 'constraint': gt_constraint})
 
+    @skipUnlessDBFeature('supports_table_check_constraints')
+    def test_add_constraint_percent_escaping(self):
+        app_label = 'add_constraint_string_quoting'
+        operations = [
+            CreateModel(
+                'Author',
+                fields=[
+                    ('id', models.AutoField(primary_key=True)),
+                    ('name', models.CharField(max_length=100)),
+                    ('rebate', models.CharField(max_length=100)),
+                ],
+            ),
+        ]
+        from_state = self.apply_operations(app_label, ProjectState(), operations)
+        # "%" generated in startswith lookup should be escaped in a way that is
+        # considered a leading wildcard.
+        check = models.Q(name__startswith='Albert')
+        constraint = models.CheckConstraint(check=check, name='name_constraint')
+        operation = migrations.AddConstraint('Author', constraint)
+        to_state = from_state.clone()
+        operation.state_forwards(app_label, to_state)
+        with connection.schema_editor() as editor:
+            operation.database_forwards(app_label, editor, from_state, to_state)
+        Author = to_state.apps.get_model(app_label, 'Author')
+        with self.assertRaises(IntegrityError), transaction.atomic():
+            Author.objects.create(name='Artur')
+        # Literal "%" should be escaped in a way that is not a considered a
+        # wildcard.
+        check = models.Q(rebate__endswith='%')
+        constraint = models.CheckConstraint(check=check, name='rebate_constraint')
+        operation = migrations.AddConstraint('Author', constraint)
+        from_state = to_state
+        to_state = from_state.clone()
+        operation.state_forwards(app_label, to_state)
+        Author = to_state.apps.get_model(app_label, 'Author')
+        with connection.schema_editor() as editor:
+            operation.database_forwards(app_label, editor, from_state, to_state)
+        Author = to_state.apps.get_model(app_label, 'Author')
+        with self.assertRaises(IntegrityError), transaction.atomic():
+            Author.objects.create(name='Albert', rebate='10$')
+        author = Author.objects.create(name='Albert', rebate='10%')
+        self.assertEqual(Author.objects.get(), author)
+
     @skipUnlessDBFeature('supports_table_check_constraints')
     def test_remove_constraint(self):
         project_state = self.set_up_test_model("test_removeconstraint", constraints=[