diff --git a/doc/source/cli/nova-manage.rst b/doc/source/cli/nova-manage.rst
index 53152a0a6fda..9556ab1bbdf4 100644
--- a/doc/source/cli/nova-manage.rst
+++ b/doc/source/cli/nova-manage.rst
@@ -1759,6 +1759,61 @@ for example.
      - The provided image property value is invalid
 
 
+Limits Commands
+===============
+
+limits migrate_to_unified_limits
+--------------------------------
+
+.. program:: nova-manage limits migrate_to_unified_limits
+
+.. code-block:: shell
+
+   nova-manage limits migrate_to_unified_limits [--project-id <project-id>]
+   [--region-id <region-id>] [--verbose] [--dry-run]
+
+Migrate quota limits from the Nova database to unified limits in Keystone.
+
+This command is useful for operators to migrate from legacy quotas to unified
+limits. Limits are migrated by copying them from the Nova database to Keystone
+by creating them using the Keystone API.
+
+.. versionadded:: 28.0.0 (2023.2 Bobcat)
+
+.. rubric:: Options
+
+.. option:: --project-id <project-id>
+
+    The project ID for which to migrate quota limits.
+
+.. option:: --region-id <region-id>
+
+    The region ID for which to migrate quota limits.
+
+.. option:: --verbose
+
+   Provide verbose output during execution.
+
+.. option:: --dry-run
+
+   Show what limits would be created without actually creating them.
+
+.. rubric:: Return codes
+
+.. list-table::
+   :widths: 20 80
+   :header-rows: 1
+
+   * - Return code
+     - Description
+   * - 0
+     - Command completed successfully
+   * - 1
+     - An unexpected error occurred
+   * - 2
+     - Failed to connect to the database
+
+
 See Also
 ========
 
diff --git a/nova/cmd/manage.py b/nova/cmd/manage.py
index d2212df2a701..bb55ed590ee7 100644
--- a/nova/cmd/manage.py
+++ b/nova/cmd/manage.py
@@ -58,6 +58,8 @@ from nova.db.main import api as db
 from nova.db import migration
 from nova import exception
 from nova.i18n import _
+from nova.limit import local as local_limit
+from nova.limit import placement as placement_limit
 from nova.network import constants
 from nova.network import neutron as neutron_api
 from nova import objects
@@ -70,6 +72,7 @@ from nova.objects import instance_mapping as instance_mapping_obj
 from nova.objects import pci_device as pci_device_obj
 from nova.objects import quotas as quotas_obj
 from nova.objects import virtual_interface as virtual_interface_obj
+import nova.quota
 from nova import rpc
 from nova.scheduler.client import report
 from nova.scheduler import utils as scheduler_utils
@@ -3367,6 +3370,183 @@ class ImagePropertyCommands:
             return 1
 
 
+class LimitsCommands():
+
+    def _create_unified_limits(self, ctxt, legacy_defaults, project_id,
+                               region_id, output, dry_run):
+        return_code = 0
+
+        # Create registered (default) limits first.
+        unified_to_legacy_names = dict(
+            **local_limit.LEGACY_LIMITS, **placement_limit.LEGACY_LIMITS)
+
+        legacy_to_unified_names = dict(
+            zip(unified_to_legacy_names.values(),
+                unified_to_legacy_names.keys()))
+
+        # For auth, a section for [keystone] is required in the config:
+        #
+        # [keystone]
+        # region_name = RegionOne
+        # user_domain_name = Default
+        # password = <password>
+        # username = <username>
+        # auth_url = http://127.0.0.1/identity
+        # auth_type = password
+        # system_scope = all
+        #
+        # The configured user needs 'role:admin and system_scope:all' by
+        # default in order to create limits in Keystone.
+        keystone_api = utils.get_sdk_adapter('identity')
+
+        # Service ID is required in unified limits APIs.
+        service_id = keystone_api.find_service('nova').id
+
+        # Retrieve the existing resource limits from Keystone.
+        registered_limits = keystone_api.registered_limits(region_id=region_id)
+
+        unified_defaults = {
+            rl.resource_name: rl.default_limit for rl in registered_limits}
+
+        # f-strings don't seem to work well with the _() translation function.
+        msg = f'Found default limits in Keystone: {unified_defaults} ...'
+        output(_(msg))
+
+        # Determine which resource limits are missing in Keystone so that we
+        # can create them.
+        output(_('Creating default limits in Keystone ...'))
+        for resource, rlimit in legacy_defaults.items():
+            resource_name = legacy_to_unified_names[resource]
+            if resource_name not in unified_defaults:
+                msg = f'Creating default limit: {resource_name} = {rlimit}'
+                if region_id:
+                    msg += f' in region {region_id}'
+                output(_(msg))
+                if not dry_run:
+                    try:
+                        keystone_api.create_registered_limit(
+                            resource_name=resource_name,
+                            default_limit=rlimit, region_id=region_id,
+                            service_id=service_id)
+                    except Exception as e:
+                        msg = f'Failed to create default limit: {str(e)}'
+                        print(_(msg))
+                        return_code = 1
+            else:
+                existing_rlimit = unified_defaults[resource_name]
+                msg = (f'A default limit: {resource_name} = {existing_rlimit} '
+                        'already exists in Keystone, skipping ...')
+                output(_(msg))
+
+        # Create project limits if there are any.
+        if not project_id:
+            return return_code
+
+        output(_('Reading project limits from the Nova API database ...'))
+        legacy_projects = objects.Quotas.get_all_by_project(ctxt, project_id)
+        legacy_projects.pop('project_id', None)
+        msg = f'Found project limits in the database: {legacy_projects} ...'
+        output(_(msg))
+
+        # Retrieve existing limits from Keystone.
+        project_limits = keystone_api.limits(
+            project_id=project_id, region_id=region_id)
+        unified_projects = {
+            pl.resource_name: pl.resource_limit for pl in project_limits}
+        msg = f'Found project limits in Keystone: {unified_projects} ...'
+        output(_(msg))
+
+        output(_('Creating project limits in Keystone ...'))
+        for resource, plimit in legacy_projects.items():
+            resource_name = legacy_to_unified_names[resource]
+            if resource_name not in unified_projects:
+                msg = (
+                    f'Creating project limit: {resource_name} = {plimit} '
+                    f'for project {project_id}')
+                if region_id:
+                    msg += f' in region {region_id}'
+                output(_(msg))
+                if not dry_run:
+                    try:
+                        keystone_api.create_limit(
+                            resource_name=resource_name,
+                            resource_limit=plimit, project_id=project_id,
+                            region_id=region_id, service_id=service_id)
+                    except Exception as e:
+                        msg = f'Failed to create project limit: {str(e)}'
+                        print(_(msg))
+                        return_code = 1
+            else:
+                existing_plimit = unified_projects[resource_name]
+                msg = (f'A project limit: {resource_name} = {existing_plimit} '
+                        'already exists in Keystone, skipping ...')
+                output(_(msg))
+
+        return return_code
+
+    @action_description(
+        _("Copy quota limits from the Nova API database to Keystone."))
+    @args('--project-id', metavar='<project-id>', dest='project_id',
+          help='Project ID for which to migrate quota limits')
+    @args('--region-id', metavar='<region-id>', dest='region_id',
+          help='Region ID for which to migrate quota limits')
+    @args('--verbose', action='store_true', dest='verbose', default=False,
+          help='Provide verbose output during execution.')
+    @args('--dry-run', action='store_true', dest='dry_run', default=False,
+          help='Show what limits would be created without actually '
+               'creating them.')
+    def migrate_to_unified_limits(self, project_id=None, region_id=None,
+                                  verbose=False, dry_run=False):
+        """Migrate quota limits from legacy quotas to unified limits.
+
+        Return codes:
+        * 0: Command completed successfully.
+        * 1: An unexpected error occurred.
+        * 2: Failed to connect to the database.
+        """
+        ctxt = context.get_admin_context()
+
+        output = lambda msg: None
+        if verbose:
+            output = lambda msg: print(msg)
+
+        output(_('Reading default limits from the Nova API database ...'))
+
+        try:
+            # This will look for limits in the 'default' quota class first and
+            # then fall back to the [quota] config options.
+            legacy_defaults = nova.quota.QUOTAS.get_defaults(ctxt)
+        except db_exc.CantStartEngineError:
+            print(_('Failed to connect to the database so aborting this '
+                    'migration attempt. Please check your config file to make '
+                    'sure that [api_database]/connection and '
+                    '[database]/connection are set and run this '
+                    'command again.'))
+            return 2
+
+        # Remove obsolete resource limits.
+        for resource in ('fixed_ips', 'floating_ips', 'security_groups',
+                         'security_group_rules'):
+            if resource in legacy_defaults:
+                msg = f'Skipping obsolete limit for {resource} ...'
+                output(_(msg))
+                legacy_defaults.pop(resource)
+
+        msg = (
+            f'Found default limits in the database: {legacy_defaults} ...')
+        output(_(msg))
+
+        try:
+            return self._create_unified_limits(
+                ctxt, legacy_defaults, project_id, region_id, output, dry_run)
+        except Exception as e:
+            msg = (f'Unexpected error, see nova-manage.log for the full '
+                   f'trace: {str(e)}')
+            print(_(msg))
+            LOG.exception('Unexpected error')
+            return 1
+
+
 CATEGORIES = {
     'api_db': ApiDbCommands,
     'cell_v2': CellV2Commands,
@@ -3375,6 +3555,7 @@ CATEGORIES = {
     'libvirt': LibvirtCommands,
     'volume_attachment': VolumeAttachmentCommands,
     'image_property': ImagePropertyCommands,
+    'limits': LimitsCommands,
 }
 
 
diff --git a/nova/conf/keystone.py b/nova/conf/keystone.py
index 73769a8a6812..f099d65d8565 100644
--- a/nova/conf/keystone.py
+++ b/nova/conf/keystone.py
@@ -28,7 +28,7 @@ keystone_group = cfg.OptGroup(
 def register_opts(conf):
     conf.register_group(keystone_group)
     confutils.register_ksa_opts(conf, keystone_group.name,
-                                DEFAULT_SERVICE_TYPE, include_auth=False)
+                                DEFAULT_SERVICE_TYPE, include_auth=True)
 
 
 def list_opts():
diff --git a/nova/tests/fixtures/nova.py b/nova/tests/fixtures/nova.py
index 4a571d68b6eb..ae2e7d70efbf 100644
--- a/nova/tests/fixtures/nova.py
+++ b/nova/tests/fixtures/nova.py
@@ -2032,3 +2032,66 @@ class GreenThreadPoolShutdownWait(fixtures.Fixture):
         self.useFixture(fixtures.MockPatch(
             'futurist.GreenThreadPoolExecutor.shutdown',
             lambda self, wait: real_shutdown(self, wait=True)))
+
+
+class UnifiedLimitsFixture(fixtures.Fixture):
+    def setUp(self):
+        super().setUp()
+        self.mock_sdk_adapter = mock.Mock()
+        real_get_sdk_adapter = utils.get_sdk_adapter
+
+        def fake_get_sdk_adapter(service_type, **kwargs):
+            if service_type == 'identity':
+                return self.mock_sdk_adapter
+            return real_get_sdk_adapter(service_type, **kwargs)
+
+        self.useFixture(fixtures.MockPatch(
+            'nova.utils.get_sdk_adapter', fake_get_sdk_adapter))
+
+        self.mock_sdk_adapter.registered_limits.side_effect = (
+            self.registered_limits)
+        self.mock_sdk_adapter.limits.side_effect = self.limits
+        self.mock_sdk_adapter.create_registered_limit.side_effect = (
+            self.create_registered_limit)
+        self.mock_sdk_adapter.create_limit.side_effect = self.create_limit
+
+        self.registered_limits_list = []
+        self.limits_list = []
+
+    def registered_limits(self, region_id=None):
+        if region_id:
+            return [rl for rl in self.registered_limits_list
+                    if rl.region_id == region_id]
+        return self.registered_limits_list
+
+    def limits(self, project_id=None, region_id=None):
+        limits_list = self.limits_list
+        if project_id:
+            limits_list = [pl for pl in limits_list
+                           if pl.project_id == project_id]
+        if region_id:
+            limits_list = [pl for pl in limits_list
+                           if pl.region_id == region_id]
+        return limits_list
+
+    def create_registered_limit(self, **attrs):
+        rl = collections.namedtuple(
+            'RegisteredLimit',
+            ['resource_name', 'default_limit', 'region_id', 'service_id'])
+        rl.resource_name = attrs.get('resource_name')
+        rl.default_limit = attrs.get('default_limit')
+        rl.region_id = attrs.get('region_id')
+        rl.service_id = attrs.get('service_id')
+        self.registered_limits_list.append(rl)
+
+    def create_limit(self, **attrs):
+        pl = collections.namedtuple(
+            'Limit',
+            ['resource_name', 'resource_limit', 'project_id', 'region_id',
+             'service_id'])
+        pl.resource_name = attrs.get('resource_name')
+        pl.resource_limit = attrs.get('resource_limit')
+        pl.project_id = attrs.get('project_id')
+        pl.region_id = attrs.get('region_id')
+        pl.service_id = attrs.get('service_id')
+        self.limits_list.append(pl)
diff --git a/nova/tests/functional/test_nova_manage.py b/nova/tests/functional/test_nova_manage.py
index 5a3f1fd5030b..5498c80a91e1 100644
--- a/nova/tests/functional/test_nova_manage.py
+++ b/nova/tests/functional/test_nova_manage.py
@@ -20,6 +20,7 @@ from unittest import mock
 import fixtures
 from neutronclient.common import exceptions as neutron_client_exc
 import os_resource_classes as orc
+from oslo_db import exception as oslo_db_exc
 from oslo_serialization import jsonutils
 from oslo_utils.fixture import uuidsentinel as uuids
 from oslo_utils import timeutils
@@ -2416,3 +2417,203 @@ class TestDBArchiveDeletedRowsMultiCellTaskLog(
         for cell_name in ('cell1', 'cell2'):
             self.assertRegex(
                 self.output.getvalue(), r'\| %s.task_log\s+\| 2' % cell_name)
+
+
+class TestNovaManageLimits(test.TestCase):
+
+    def setUp(self):
+        super().setUp()
+        self.ctxt = context.get_admin_context()
+        self.cli = manage.LimitsCommands()
+        self.output = StringIO()
+        self.useFixture(fixtures.MonkeyPatch('sys.stdout', self.output))
+        self.ul_api = self.useFixture(nova_fixtures.UnifiedLimitsFixture())
+
+    @mock.patch('nova.quota.QUOTAS.get_defaults')
+    def test_migrate_to_unified_limits_no_db_access(self, mock_get_defaults):
+        mock_get_defaults.side_effect = oslo_db_exc.CantStartEngineError()
+        return_code = self.cli.migrate_to_unified_limits(verbose=True)
+        self.assertEqual(2, return_code)
+
+    @mock.patch('nova.utils.get_sdk_adapter')
+    def test_migrate_to_unified_limits_unexpected_error(self, mock_sdk):
+        # Simulate an error creating limits.
+        mock_sdk.return_value.create_registered_limit.side_effect = (
+            test.TestingException('oops!'))
+        mock_sdk.return_value.create_limit.side_effect = (
+            test.TestingException('oops!'))
+
+        # Create a couple of project limits.
+        objects.Quotas.create_limit(self.ctxt, uuids.project, 'ram', 8192)
+        objects.Quotas.create_limit(self.ctxt, uuids.project, 'instances', 25)
+
+        return_code = self.cli.migrate_to_unified_limits(
+            project_id=uuids.project, verbose=True)
+        self.assertEqual(1, return_code)
+
+        # Verify that limit create attempts for other resources were attempted
+        # after an unexpected error.
+        #
+        # There are 10 default limit values in the config options: instances,
+        # cores, ram, metadata_items, injected_files,
+        # injected_file_content_bytes, injected_file_path_length, key_pairs,
+        # server_groups, and server_group_members.
+        self.assertEqual(
+            10, mock_sdk.return_value.create_registered_limit.call_count)
+
+        self.assertEqual(2, mock_sdk.return_value.create_limit.call_count)
+
+    def test_migrate_to_unified_limits_already_exists(self):
+        # Create a couple of unified limits to already exist.
+        self.ul_api.create_registered_limit(
+            resource_name='servers', default_limit=8)
+        self.ul_api.create_limit(
+            resource_name='class:VCPU', resource_limit=6,
+            project_id=uuids.project)
+
+        # Create a couple of project limits.
+        objects.Quotas.create_limit(self.ctxt, uuids.project, 'cores', 10)
+        objects.Quotas.create_limit(self.ctxt, uuids.project, 'instances', 25)
+
+        self.cli.migrate_to_unified_limits(
+            project_id=uuids.project, verbose=True)
+
+        # There are 10 default limit values in the config options, so because a
+        # limit for 'servers' already exists, we should have only created 9.
+        mock_sdk = self.ul_api.mock_sdk_adapter
+        self.assertEqual(
+            9, mock_sdk.create_registered_limit.call_count)
+
+        # There already exists a project limit for 'class:VCPU', so we should
+        # have created only 1 project limit.
+        self.assertEqual(1, mock_sdk.create_limit.call_count)
+
+    def test_migrate_to_unified_limits(self):
+        # Set some defaults using the config options.
+        self.flags(instances=5, group='quota')
+        self.flags(cores=22, group='quota')
+        self.flags(ram=4096, group='quota')
+        self.flags(metadata_items=64, group='quota')
+        self.flags(injected_files=3, group='quota')
+        self.flags(injected_file_content_bytes=9 * 1024, group='quota')
+        self.flags(injected_file_path_length=250, group='quota')
+        self.flags(key_pairs=50, group='quota')
+        self.flags(server_groups=7, group='quota')
+        self.flags(server_group_members=12, group='quota')
+        # Create a couple of defaults via the 'default' quota class. These take
+        # precedence over the config option values.
+        objects.Quotas.create_class(self.ctxt, 'default', 'cores', 10)
+        objects.Quotas.create_class(self.ctxt, 'default', 'key_pairs', 75)
+        # Create obsolete limits which should not be migrated to unified
+        # limits.
+        objects.Quotas.create_class(self.ctxt, 'default', 'fixed_ips', 8)
+        objects.Quotas.create_class(self.ctxt, 'default', 'floating_ips', 6)
+        objects.Quotas.create_class(self.ctxt, 'default', 'security_groups', 4)
+        objects.Quotas.create_class(
+            self.ctxt, 'default', 'security_group_rules', 14)
+        # Create a couple of project limits.
+        objects.Quotas.create_limit(self.ctxt, uuids.project, 'ram', 8192)
+        objects.Quotas.create_limit(self.ctxt, uuids.project, 'instances', 25)
+
+        # Verify there are no unified limits yet.
+        registered_limits = self.ul_api.registered_limits()
+        self.assertEqual(0, len(registered_limits))
+        limits = self.ul_api.limits(project_id=uuids.project)
+        self.assertEqual(0, len(limits))
+
+        # Verify that --dry-run works to not actually create limits.
+        self.cli.migrate_to_unified_limits(dry_run=True)
+
+        # There should still be no unified limits yet.
+        registered_limits = self.ul_api.registered_limits()
+        self.assertEqual(0, len(registered_limits))
+        limits = self.ul_api.limits(project_id=uuids.project)
+        self.assertEqual(0, len(limits))
+
+        # Migrate the limits.
+        self.cli.migrate_to_unified_limits(
+            project_id=uuids.project, verbose=True)
+
+        # There should be 10 registered (default) limits now.
+        expected_registered_limits = {
+            'servers': 5,
+            'class:VCPU': 10,
+            'class:MEMORY_MB': 4096,
+            'server_metadata_items': 64,
+            'server_injected_files': 3,
+            'server_injected_file_content_bytes': 9 * 1024,
+            'server_injected_file_path_bytes': 250,
+            'server_key_pairs': 75,
+            'server_groups': 7,
+            'server_group_members': 12,
+        }
+
+        registered_limits = self.ul_api.registered_limits()
+        self.assertEqual(10, len(registered_limits))
+        for rl in registered_limits:
+            self.assertEqual(
+                expected_registered_limits[rl.resource_name], rl.default_limit)
+
+        # And 2 project limits.
+        expected_limits = {
+            'class:MEMORY_MB': 8192,
+            'servers': 25,
+        }
+
+        limits = self.ul_api.limits(project_id=uuids.project)
+        self.assertEqual(2, len(limits))
+        for pl in limits:
+            self.assertEqual(
+                expected_limits[pl.resource_name], pl.resource_limit)
+
+        # Verify there are no project limits for a different project.
+        other_project_limits = self.ul_api.limits(
+            project_id=uuids.otherproject)
+        self.assertEqual(0, len(other_project_limits))
+
+        # Try migrating limits for a specific region.
+        region_registered_limits = self.ul_api.registered_limits(
+            region_id=uuids.region)
+        self.assertEqual(0, len(region_registered_limits))
+
+        self.cli.migrate_to_unified_limits(
+            region_id=uuids.region, verbose=True)
+
+        region_registered_limits = self.ul_api.registered_limits(
+            region_id=uuids.region)
+        self.assertEqual(10, len(region_registered_limits))
+        for rl in region_registered_limits:
+            self.assertEqual(
+                expected_registered_limits[rl.resource_name], rl.default_limit)
+
+        # Try migrating project limits for that region.
+        region_limits = self.ul_api.limits(
+            project_id=uuids.project, region_id=uuids.region)
+        self.assertEqual(0, len(region_limits))
+
+        self.cli.migrate_to_unified_limits(
+            project_id=uuids.project, region_id=uuids.region, verbose=True)
+
+        region_limits = self.ul_api.limits(
+            project_id=uuids.project, region_id=uuids.region)
+        self.assertEqual(2, len(region_limits))
+        for pl in region_limits:
+            self.assertEqual(
+                expected_limits[pl.resource_name], pl.resource_limit)
+
+        # Verify no --verbose outputs nothing, migrate limits for a different
+        # project after clearing stdout.
+        self.output = StringIO()
+        self.assertEqual('', self.output.getvalue())
+
+        # Create a limit for the other project.
+        objects.Quotas.create_limit(self.ctxt, uuids.otherproject, 'ram', 2048)
+
+        self.cli.migrate_to_unified_limits(project_id=uuids.otherproject)
+
+        other_project_limits = self.ul_api.limits(
+            project_id=uuids.otherproject)
+        self.assertEqual(1, len(other_project_limits))
+
+        # Output should still be empty after migrating.
+        self.assertEqual('', self.output.getvalue())
diff --git a/releasenotes/notes/nova-manage-limits-migrate-d1de95d20991674c.yaml b/releasenotes/notes/nova-manage-limits-migrate-d1de95d20991674c.yaml
new file mode 100644
index 000000000000..372142ccf15b
--- /dev/null
+++ b/releasenotes/notes/nova-manage-limits-migrate-d1de95d20991674c.yaml
@@ -0,0 +1,7 @@
+features:
+  - |
+    A new command ``nova-manage limits migrate_to_unified_limits`` has been
+    added to make migration from the ``nova.quota.DbQuotaDriver`` to the
+    ``nova.quota.UnifiedLimitsDriver`` easier. This will enable operators to
+    have their existing quota limits copied from the Nova database to Keystone
+    automatically.