diff --git a/neutron_lib/api/definitions/__init__.py b/neutron_lib/api/definitions/__init__.py
index f919d4f29..fc14383c6 100644
--- a/neutron_lib/api/definitions/__init__.py
+++ b/neutron_lib/api/definitions/__init__.py
@@ -60,6 +60,7 @@ from neutron_lib.api.definitions import qos_rule_type_details
 from neutron_lib.api.definitions import router_availability_zone
 from neutron_lib.api.definitions import router_interface_fip
 from neutron_lib.api.definitions import routerservicetype
+from neutron_lib.api.definitions import segment
 from neutron_lib.api.definitions import servicetype
 from neutron_lib.api.definitions import sorting
 from neutron_lib.api.definitions import subnet
@@ -121,6 +122,7 @@ _ALL_API_DEFINITIONS = {
     router_availability_zone,
     router_interface_fip,
     routerservicetype,
+    segment,
     servicetype,
     sorting,
     subnet,
diff --git a/neutron_lib/api/definitions/segment.py b/neutron_lib/api/definitions/segment.py
new file mode 100644
index 000000000..71d6cd703
--- /dev/null
+++ b/neutron_lib/api/definitions/segment.py
@@ -0,0 +1,123 @@
+# Copyright (c) 2016 Hewlett Packard Enterprise Development Company, L.P.
+#
+#    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
+from neutron_lib.api.definitions import provider_net
+from neutron_lib.api.definitions import subnet
+from neutron_lib import constants
+from neutron_lib.db import constants as db_constants
+
+
+SEGMENT_ID = 'segment_id'
+NETWORK_TYPE = 'network_type'
+PHYSICAL_NETWORK = 'physical_network'
+SEGMENTATION_ID = 'segmentation_id'
+NAME_LEN = db_constants.NAME_FIELD_SIZE
+DESC_LEN = db_constants.DESCRIPTION_FIELD_SIZE
+
+ALIAS = 'segment'
+IS_SHIM_EXTENSION = False
+IS_STANDARD_ATTR_EXTENSION = False
+NAME = 'Segment'
+API_PREFIX = ''
+DESCRIPTION = 'Segments extension.'
+UPDATED_TIMESTAMP = '2016-02-24T17:00:00-00:00'
+RESOURCE_NAME = 'segment'
+COLLECTION_NAME = RESOURCE_NAME + 's'
+RESOURCE_ATTRIBUTE_MAP = {
+    COLLECTION_NAME: {
+        'id': {
+            'allow_post': False,
+            'allow_put': False,
+            'validate': {
+                'type:uuid': None
+            },
+            'is_visible': True,
+            'primary_key': True
+        },
+        'tenant_id': {
+            'allow_post': True,
+            'allow_put': False,
+            'validate': {
+                'type:string': db_constants.PROJECT_ID_FIELD_SIZE
+            },
+            'is_visible': False},
+        'network_id': {
+            'allow_post': True,
+            'allow_put': False,
+            'validate': {
+                'type:uuid': None
+            },
+            'is_visible': True
+        },
+        PHYSICAL_NETWORK: {
+            'allow_post': True,
+            'allow_put': False,
+            'default': constants.ATTR_NOT_SPECIFIED,
+            'validate': {
+                'type:string': provider_net.PHYSICAL_NETWORK_MAX_LEN
+            },
+            'is_visible': True
+        },
+        NETWORK_TYPE: {
+            'allow_post': True,
+            'allow_put': False,
+            'validate': {
+                'type:string': provider_net.NETWORK_TYPE_MAX_LEN
+            },
+            'is_visible': True
+        },
+        SEGMENTATION_ID: {
+            'allow_post': True,
+            'allow_put': False,
+            'default': constants.ATTR_NOT_SPECIFIED,
+            'convert_to': converters.convert_to_int,
+            'is_visible': True
+        },
+        'name': {
+            'allow_post': True,
+            'allow_put': True,
+            'default': constants.ATTR_NOT_SPECIFIED,
+            'validate': {
+                'type:string_or_none': NAME_LEN
+            },
+            'is_visible': True
+        },
+        'description': {
+            'allow_post': True,
+            'allow_put': True,
+            'default': constants.ATTR_NOT_SPECIFIED,
+            'validate': {
+                'type:string_or_none': DESC_LEN
+            },
+            'is_visible': True
+        }
+    },
+    subnet.COLLECTION_NAME: {
+        SEGMENT_ID: {
+            'allow_post': True,
+            'allow_put': False,
+            'default': None,
+            'validate': {
+                'type:uuid_or_none': None
+            },
+            'is_visible': True
+        }
+    }
+}
+SUB_RESOURCE_ATTRIBUTE_MAP = {}
+ACTION_MAP = {}
+REQUIRED_EXTENSIONS = []
+OPTIONAL_EXTENSIONS = []
+ACTION_STATUS = {}
diff --git a/neutron_lib/tests/unit/api/definitions/test_segment.py b/neutron_lib/tests/unit/api/definitions/test_segment.py
new file mode 100644
index 000000000..eb374a0ca
--- /dev/null
+++ b/neutron_lib/tests/unit/api/definitions/test_segment.py
@@ -0,0 +1,22 @@
+#    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 segment
+from neutron_lib.tests.unit.api.definitions import base
+
+
+class SegmentDefinitionTestCase(base.DefinitionBaseTestCase):
+    extension_module = segment
+    extension_resources = (segment.COLLECTION_NAME,)
+    extension_attributes = ('network_id', segment.PHYSICAL_NETWORK,
+                            segment.NETWORK_TYPE, segment.SEGMENTATION_ID,
+                            segment.SEGMENT_ID,)
diff --git a/releasenotes/notes/rehome-segment-apidef-a5f81adb834328f8.yaml b/releasenotes/notes/rehome-segment-apidef-a5f81adb834328f8.yaml
new file mode 100644
index 000000000..592a9f145
--- /dev/null
+++ b/releasenotes/notes/rehome-segment-apidef-a5f81adb834328f8.yaml
@@ -0,0 +1,4 @@
+---
+features:
+  - The ``segment`` extension's API definition is now available in
+    ``neutron_lib.api.definitions.segment``.