diff --git a/api-ref/source/v2/parameters.yaml b/api-ref/source/v2/parameters.yaml
index e7e866c02..c50148f89 100644
--- a/api-ref/source/v2/parameters.yaml
+++ b/api-ref/source/v2/parameters.yaml
@@ -5500,6 +5500,12 @@ state:
   in: body
   required: true
   type: string
+stateful_enabled:
+  description: |
+    Indicates if the security group is stateful or stateless.
+  in: body
+  required: false
+  type: boolean
 status_description:
   description: |
     Human-readable description of the status.
diff --git a/api-ref/source/v2/samples/security-groups/security-group-create-request.json b/api-ref/source/v2/samples/security-groups/security-group-create-request.json
index 8a93ef934..44bb8b7e5 100644
--- a/api-ref/source/v2/samples/security-groups/security-group-create-request.json
+++ b/api-ref/source/v2/samples/security-groups/security-group-create-request.json
@@ -1,6 +1,7 @@
 {
     "security_group": {
         "name": "new-webservers",
-        "description": "security group for webservers"
+        "description": "security group for webservers",
+        "stateful": true
     }
 }
diff --git a/api-ref/source/v2/samples/security-groups/security-group-create-response.json b/api-ref/source/v2/samples/security-groups/security-group-create-response.json
index 74416c7a9..31a91fc27 100644
--- a/api-ref/source/v2/samples/security-groups/security-group-create-response.json
+++ b/api-ref/source/v2/samples/security-groups/security-group-create-response.json
@@ -47,6 +47,7 @@
         "updated_at": "2018-03-19T19:16:56Z",
         "revision_number": 1,
         "tags": ["tag1,tag2"],
-        "tenant_id": "e4f50856753b4dc6afee5fa6b9b6c550"
+        "tenant_id": "e4f50856753b4dc6afee5fa6b9b6c550",
+        "stateful": true
     }
 }
diff --git a/api-ref/source/v2/samples/security-groups/security-group-show-response.json b/api-ref/source/v2/samples/security-groups/security-group-show-response.json
index a411fef04..a1aed4b06 100644
--- a/api-ref/source/v2/samples/security-groups/security-group-show-response.json
+++ b/api-ref/source/v2/samples/security-groups/security-group-show-response.json
@@ -82,6 +82,7 @@
         "updated_at": "2018-03-19T19:16:56Z",
         "revision_number": 4,
         "tags": ["tag1,tag2"],
-        "tenant_id": "e4f50856753b4dc6afee5fa6b9b6c550"
+        "tenant_id": "e4f50856753b4dc6afee5fa6b9b6c550",
+        "stateful": true
     }
 }
diff --git a/api-ref/source/v2/samples/security-groups/security-group-update-request.json b/api-ref/source/v2/samples/security-groups/security-group-update-request.json
index 67bfda27c..44e2036a7 100644
--- a/api-ref/source/v2/samples/security-groups/security-group-update-request.json
+++ b/api-ref/source/v2/samples/security-groups/security-group-update-request.json
@@ -1,6 +1,7 @@
 {
     "security_group": {
         "name": "mysecgroup",
-        "description": "my security group"
+        "description": "my security group",
+        "stateful": true
     }
 }
diff --git a/api-ref/source/v2/samples/security-groups/security-group-update-response.json b/api-ref/source/v2/samples/security-groups/security-group-update-response.json
index d94141610..e2b1cf4fe 100644
--- a/api-ref/source/v2/samples/security-groups/security-group-update-response.json
+++ b/api-ref/source/v2/samples/security-groups/security-group-update-response.json
@@ -9,6 +9,7 @@
         "id": "01fbade5-b664-42f6-83ae-4e214f4263fa",
         "name": "mysecgroup",
         "description": "my security group",
-        "tags": ["tag1,tag2"]
+        "tags": ["tag1,tag2"],
+        "stateful": true
     }
 }
diff --git a/api-ref/source/v2/samples/security-groups/security-groups-list-response.json b/api-ref/source/v2/samples/security-groups/security-groups-list-response.json
index b4b9506e6..642c63e72 100644
--- a/api-ref/source/v2/samples/security-groups/security-groups-list-response.json
+++ b/api-ref/source/v2/samples/security-groups/security-groups-list-response.json
@@ -83,7 +83,8 @@
             "created_at": "2018-03-19T19:16:56Z",
             "updated_at": "2018-03-19T19:16:56Z",
             "tags": ["tag1,tag2"],
-            "tenant_id": "e4f50856753b4dc6afee5fa6b9b6c550"
+            "tenant_id": "e4f50856753b4dc6afee5fa6b9b6c550",
+            "stateful": true
         }
     ]
 }
diff --git a/api-ref/source/v2/security-groups.inc b/api-ref/source/v2/security-groups.inc
index d0c10c33c..230d51ce3 100644
--- a/api-ref/source/v2/security-groups.inc
+++ b/api-ref/source/v2/security-groups.inc
@@ -20,6 +20,14 @@ The ``standard-attr-tag`` adds Tag support for resources with
 standard attributes by adding the ``tags`` attribute
 allowing consumers to associate tags with resources.
 
+Stateful security groups extension (``stateful-security-group``)
+================================================================
+
+The stateful security group extension (``stateful-security-group``) adds the
+``stateful`` field to security groups, allowing users to configure stateful
+or stateless security groups for ``ports``. The existing security groups
+will all be considered as stateful. Update of the ``stateful`` attribute is
+allowed when there is no port associated with the security group.
 
 List security groups
 ====================
@@ -76,6 +84,7 @@ Response Parameters
    - description: description
    - security_group_rules: security_group_rules
    - tags: tags
+   - stateful: stateful_enabled
 
 Response Example
 ----------------
@@ -107,6 +116,7 @@ Request
    - project_id: project_id
    - description: description-request
    - name: name
+   - stateful: stateful_enabled
 
 Request Example
 ---------------
@@ -130,6 +140,7 @@ Response Parameters
    - description: description
    - security_group_rules: security_group_rules
    - tags: tags
+   - stateful: stateful_enabled
 
 Response Example
 ----------------
@@ -181,6 +192,7 @@ Response Parameters
    - description: description
    - security_group_rules: security_group_rules
    - tags: tags
+   - stateful: stateful_enabled
 
 Response Example
 ----------------
@@ -231,6 +243,7 @@ Response Parameters
    - description: description
    - security_group_rules: security_group_rules
    - tags: tags
+   - stateful: stateful_enabled
 
 Response Example
 ----------------
diff --git a/neutron_lib/api/definitions/__init__.py b/neutron_lib/api/definitions/__init__.py
index 04ba25666..f522a9d4b 100644
--- a/neutron_lib/api/definitions/__init__.py
+++ b/neutron_lib/api/definitions/__init__.py
@@ -96,6 +96,7 @@ from neutron_lib.api.definitions import sfc
 from neutron_lib.api.definitions import sort_key_validation
 from neutron_lib.api.definitions import sorting
 from neutron_lib.api.definitions import standard_attr_segment
+from neutron_lib.api.definitions import stateful_security_group
 from neutron_lib.api.definitions import subnet
 from neutron_lib.api.definitions import subnet_dns_publish_fixed_ip
 from neutron_lib.api.definitions import subnet_onboard
@@ -200,6 +201,7 @@ _ALL_API_DEFINITIONS = {
     sort_key_validation,
     sorting,
     standard_attr_segment,
+    stateful_security_group,
     subnet,
     subnet_dns_publish_fixed_ip,
     subnet_onboard,
diff --git a/neutron_lib/api/definitions/base.py b/neutron_lib/api/definitions/base.py
index a4dd0aab5..4ab079402 100644
--- a/neutron_lib/api/definitions/base.py
+++ b/neutron_lib/api/definitions/base.py
@@ -55,7 +55,8 @@ KNOWN_RESOURCES = (
     'ports',
     'routers',
     'subnets',
-    'subnetpools'
+    'subnetpools',
+    'security_groups'
 )
 
 KNOWN_HTTP_ACTIONS = (
diff --git a/neutron_lib/api/definitions/stateful_security_group.py b/neutron_lib/api/definitions/stateful_security_group.py
new file mode 100644
index 000000000..b056d85f7
--- /dev/null
+++ b/neutron_lib/api/definitions/stateful_security_group.py
@@ -0,0 +1,61 @@
+# Copyright 2018 NOKIA
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+
+from neutron_lib.api import converters
+
+
+# The alias of the extension.
+ALIAS = 'stateful-security-group'
+
+IS_SHIM_EXTENSION = False
+
+IS_STANDARD_ATTR_EXTENSION = False
+
+# The name of the extension.
+NAME = 'Stateful security group'
+
+# The description of the extension.
+DESCRIPTION = "Indicates if the security group is stateful or not"
+
+# A timestamp of when the extension was introduced.
+UPDATED_TIMESTAMP = "2019-11-26T09:00:00-00:00"
+
+# The resource attribute map for the extension.
+RESOURCE_ATTRIBUTE_MAP = {
+    'security_groups': {
+        'stateful': {'allow_post': True, 'allow_put': True,
+                     'is_visible': True, 'default': True,
+                     'convert_to': converters.convert_to_boolean}
+    }
+}
+
+# The subresource attribute map for the extension.
+SUB_RESOURCE_ATTRIBUTE_MAP = {
+}
+
+# The action map.
+ACTION_MAP = {
+}
+
+# The action status.
+ACTION_STATUS = {
+}
+
+# The list of required extensions.
+REQUIRED_EXTENSIONS = ['security-group']
+
+# The list of optional extensions.
+OPTIONAL_EXTENSIONS = [
+]
diff --git a/neutron_lib/tests/unit/api/definitions/test_stateful_security_group.py b/neutron_lib/tests/unit/api/definitions/test_stateful_security_group.py
new file mode 100644
index 000000000..bd7c17ef8
--- /dev/null
+++ b/neutron_lib/tests/unit/api/definitions/test_stateful_security_group.py
@@ -0,0 +1,23 @@
+# Copyright 2018 NOKIA
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+
+from neutron_lib.api.definitions import stateful_security_group
+from neutron_lib.tests.unit.api.definitions import base
+
+
+class StatefulSecurityGroupDefinitionTestCase(base.DefinitionBaseTestCase):
+
+    extension_module = stateful_security_group
+    extension_attributes = ('stateful',)
diff --git a/releasenotes/notes/stateful-security-group-a1ece5472f029dc1.yaml b/releasenotes/notes/stateful-security-group-a1ece5472f029dc1.yaml
new file mode 100644
index 000000000..fde687a43
--- /dev/null
+++ b/releasenotes/notes/stateful-security-group-a1ece5472f029dc1.yaml
@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    The API defintion for the ``stateful-security-group`` extension is
+    now available in ``neutron_lib.api.definitions.stateful_security_group``.
\ No newline at end of file