diff --git a/api-ref/source/v3/ext-backups.inc b/api-ref/source/v3/ext-backups.inc
index 41b2b5f1eea..be003de743d 100644
--- a/api-ref/source/v3/ext-backups.inc
+++ b/api-ref/source/v3/ext-backups.inc
@@ -97,6 +97,7 @@ Response Parameters
    - os-backup-project-attr:project_id: os-backup-project-attr:project_id
    - count: count
    - metadata: metadata_backup
+   - user_id: user_id_backup
 
 Response Example
 ----------------
@@ -155,6 +156,7 @@ Response Parameters
    - snapshot_id: snapshot_id_source_vol
    - os-backup-project-attr:project_id: os-backup-project-attr:project_id
    - metadata: metadata_backup
+   - user_id: user_id_backup
 
 Response Example
 ----------------
diff --git a/api-ref/source/v3/parameters.yaml b/api-ref/source/v3/parameters.yaml
index 54d051122a3..7288b757714 100644
--- a/api-ref/source/v3/parameters.yaml
+++ b/api-ref/source/v3/parameters.yaml
@@ -2766,6 +2766,13 @@ user_id:
   in: body
   required: true
   type: string
+user_id_backup:
+  description: |
+    The UUID of the project owner.
+  in: body
+  required: true
+  type: string
+  min_version: 3.56
 user_id_min:
   description: |
     The UUID of the user.
diff --git a/api-ref/source/v3/samples/backup-show-response.json b/api-ref/source/v3/samples/backup-show-response.json
index 8b112f51171..e400ada9b9c 100644
--- a/api-ref/source/v3/samples/backup-show-response.json
+++ b/api-ref/source/v3/samples/backup-show-response.json
@@ -19,6 +19,7 @@
         "name": "backup001",
         "object_count": 22,
         "os-backup-project-attr:project_id": "2c67a14be9314c5dae2ee6c4ec90cf0b",
+        "user_id": "515ba0dd59f84f25a6a084a45d8d93b2",
         "size": 1,
         "updated_at": "2013-04-20T05:30:19.000000",
         "data_timestamp": "2013-04-20T05:30:19.000000",
diff --git a/api-ref/source/v3/samples/backups-list-detailed-response.json b/api-ref/source/v3/samples/backups-list-detailed-response.json
index 6cf72cf9e51..16acc8d8329 100644
--- a/api-ref/source/v3/samples/backups-list-detailed-response.json
+++ b/api-ref/source/v3/samples/backups-list-detailed-response.json
@@ -20,6 +20,7 @@
             "name": "backup001",
             "object_count": 22,
             "os-backup-project-attr:project_id": "2c67a14be9314c5dae2ee6c4ec90cf0b",
+            "user_id": "515ba0dd59f84f25a6a084a45d8d93b2",
             "size": 1,
             "status": "available",
             "updated_at": "2013-04-02T10:35:27.000000",
@@ -49,6 +50,7 @@
             "name": "backup002",
             "object_count": 22,
             "os-backup-project-attr:project_id": "2c67a14be9314c5dae2ee6c4ec90cf0b",
+            "user_id": "515ba0dd59f84f25a6a084a45d8d93b2",
             "size": 1,
             "status": "available",
             "updated_at": "2013-04-02T10:21:48.000000",
diff --git a/cinder/api/microversions.py b/cinder/api/microversions.py
index 620aa9f7ee3..bdbf0966166 100644
--- a/cinder/api/microversions.py
+++ b/cinder/api/microversions.py
@@ -151,6 +151,8 @@ ATTACHMENT_CREATE_MODE_ARG = '3.54'
 
 TRANSFER_WITH_SNAPSHOTS = '3.55'
 
+BACKUP_PROJECT_USER_ID = '3.56'
+
 
 def get_mv_header(version):
     """Gets a formatted HTTP microversion header.
diff --git a/cinder/api/openstack/api_version_request.py b/cinder/api/openstack/api_version_request.py
index a72111fb16f..05abf4160f3 100644
--- a/cinder/api/openstack/api_version_request.py
+++ b/cinder/api/openstack/api_version_request.py
@@ -127,6 +127,8 @@ REST_API_VERSION_HISTORY = """
              Also, additional parameters will not be allowed.
     * 3.54 - Add ``mode`` argument to attachment-create.
     * 3.55 - Support transfer volume with snapshots
+    * 3.56 - Add ``user_id`` attribute to response body of list backup with
+             detail and show backup detail APIs.
 """
 
 # The minimum and maximum versions of the API supported
@@ -134,7 +136,7 @@ REST_API_VERSION_HISTORY = """
 # minimum version of the API supported.
 # Explicitly using /v2 endpoints will still work
 _MIN_API_VERSION = "3.0"
-_MAX_API_VERSION = "3.55"
+_MAX_API_VERSION = "3.56"
 _LEGACY_API_VERSION2 = "2.0"
 UPDATED = "2018-07-17T00:00:00Z"
 
diff --git a/cinder/api/openstack/rest_api_version_history.rst b/cinder/api/openstack/rest_api_version_history.rst
index 237f4adde2e..a4fa8a5b2ee 100644
--- a/cinder/api/openstack/rest_api_version_history.rst
+++ b/cinder/api/openstack/rest_api_version_history.rst
@@ -441,3 +441,8 @@ Add ``mode`` argument to attachment-create.
 3.55 (Maximum in Rocky)
 -----------------------
 Support ability to transfer snapshots along with their parent volume.
+
+3.56
+----
+Add ``user_id`` attribute to response body of list backup with detail and show
+backup detail APIs.
diff --git a/cinder/api/v3/backups.py b/cinder/api/v3/backups.py
index e31d0c3ac62..83dc713f2e7 100644
--- a/cinder/api/v3/backups.py
+++ b/cinder/api/v3/backups.py
@@ -65,6 +65,11 @@ class BackupsController(backups_v2.BackupsController):
         key = "os-backup-project-attr:project_id"
         backup[key] = db_backup['project_id']
 
+    def _add_backup_user_attribute(self, req, backup):
+        db_backup = req.get_db_backup(backup['id'])
+        key = "user_id"
+        backup[key] = db_backup['user_id']
+
     def show(self, req, id):
         """Return data about the given backup."""
         LOG.debug('Show backup with id %s.', id)
@@ -79,6 +84,10 @@ class BackupsController(backups_v2.BackupsController):
         if req_version.matches(mv.BACKUP_PROJECT):
             if context.authorize(policy.BACKUP_ATTRIBUTES_POLICY, fatal=False):
                 self._add_backup_project_attribute(req, resp_backup['backup'])
+
+        if req_version.matches(mv.BACKUP_PROJECT_USER_ID):
+            if context.authorize(policy.BACKUP_ATTRIBUTES_POLICY, fatal=False):
+                self._add_backup_user_attribute(req, resp_backup['backup'])
         return resp_backup
 
     def detail(self, req):
@@ -90,6 +99,11 @@ class BackupsController(backups_v2.BackupsController):
             if context.authorize(policy.BACKUP_ATTRIBUTES_POLICY, fatal=False):
                 for bak in resp_backup['backups']:
                     self._add_backup_project_attribute(req, bak)
+
+        if req_version.matches(mv.BACKUP_PROJECT_USER_ID):
+            if context.authorize(policy.BACKUP_ATTRIBUTES_POLICY, fatal=False):
+                for bak in resp_backup['backups']:
+                    self._add_backup_user_attribute(req, bak)
         return resp_backup
 
     def _convert_sort_name(self, req_version, sort_keys):
diff --git a/cinder/tests/unit/api/contrib/test_backup_project_attribute.py b/cinder/tests/unit/api/contrib/test_backup_project_attribute.py
index e48295c5e45..b3c1974a0b3 100644
--- a/cinder/tests/unit/api/contrib/test_backup_project_attribute.py
+++ b/cinder/tests/unit/api/contrib/test_backup_project_attribute.py
@@ -33,6 +33,7 @@ def fake_backup_get(*args, **kwargs):
     bak = {
         'id': fake.BACKUP_ID,
         'project_id': fake.PROJECT_ID,
+        'user_id': fake.USER_ID,
     }
     return fake_backup.fake_backup_obj(ctx, **bak)
 
@@ -101,3 +102,30 @@ class BackupProjectAttributeTest(test.TestCase):
         bak = self._send_backup_request(
             ctx, version=mv.get_prior_version(mv.BACKUP_PROJECT))
         self.assertNotIn('os-backup-project-attr:project_id', bak)
+
+    @ddt.data(True, False)
+    def test_get_backup_with_user_id(self, is_admin):
+        ctx = context.RequestContext(fake.USER_ID, fake.PROJECT_ID, is_admin)
+        bak = self._send_backup_request(ctx,
+                                        version=mv.BACKUP_PROJECT_USER_ID)
+        if is_admin:
+            self.assertEqual(fake.USER_ID, bak['user_id'])
+        else:
+            self.assertNotIn('user_id', bak)
+
+    @ddt.data(True, False)
+    def test_list_detail_backups_with_user_id(self, is_admin):
+        ctx = context.RequestContext(fake.USER_ID, fake.PROJECT_ID, is_admin)
+        baks = self._send_backup_request(ctx, detail=True,
+                                         version=mv.BACKUP_PROJECT_USER_ID)
+        if is_admin:
+            self.assertEqual(fake.USER_ID,
+                             baks[0]['user_id'])
+        else:
+            self.assertNotIn('user_id', baks[0])
+
+    def test_get_backup_user_id_before_microversion_v356(self):
+        ctx = context.RequestContext(fake.USER_ID, fake.PROJECT_ID, True)
+        bak = self._send_backup_request(
+            ctx, version=mv.get_prior_version(mv.BACKUP_PROJECT_USER_ID))
+        self.assertNotIn('user_id', bak)
diff --git a/cinder/tests/unit/backup/fake_backup.py b/cinder/tests/unit/backup/fake_backup.py
index 41379095c30..314b95b4712 100644
--- a/cinder/tests/unit/backup/fake_backup.py
+++ b/cinder/tests/unit/backup/fake_backup.py
@@ -34,6 +34,10 @@ def fake_db_backup(**updates):
         'service': 'fake_service',
         'object_count': 5,
         'num_dependent_backups': 0,
+        'backup_metadata': [
+            {'key': 'key1', 'value': 'value1'},
+            {'key': 'key2', 'value': 'value2'}
+        ],
     }
 
     for name, field in objects.Backup.fields.items():
@@ -54,4 +58,5 @@ def fake_db_backup(**updates):
 
 def fake_backup_obj(context, **updates):
     return objects.Backup._from_db_object(context, objects.Backup(),
-                                          fake_db_backup(**updates))
+                                          fake_db_backup(**updates),
+                                          expected_attrs=['metadata'])
diff --git a/releasenotes/notes/add-user-id-attribute-to-backup-response-ce27364680c895f7.yaml b/releasenotes/notes/add-user-id-attribute-to-backup-response-ce27364680c895f7.yaml
new file mode 100644
index 00000000000..12c90b8a6a1
--- /dev/null
+++ b/releasenotes/notes/add-user-id-attribute-to-backup-response-ce27364680c895f7.yaml
@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    Add ``user_id`` attribute to response body of list backup with detail
+    and show backup detail APIs.