diff --git a/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/maintenance.py b/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/maintenance.py
index 9927767997c..d104f767beb 100644
--- a/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/maintenance.py
+++ b/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/maintenance.py
@@ -1030,6 +1030,63 @@ class DBInconsistenciesPeriodics(SchemaAwarePeriodicsBase):
                                                    from_reload=True)
         raise periodics.NeverAgain()
 
+    @periodics.periodic(spacing=300, run_immediately=True)
+    def remove_duplicated_chassis_registers(self):
+        """Remove the "Chassis" and "Chassis_Private" duplicated registers.
+
+        When the ovn-controller service of a node is updated and the system-id
+        is changed, if the old service is not stopped gracefully, it will leave
+        a "Chassis" and a "Chassis_Private" registers on the OVN SB database.
+        These leftovers must be removed.
+
+        NOTE: this method is executed every 5 minutes. If a new chassis is
+        added, this method will perform again the clean-up process.
+
+        NOTE: this method can be executed only if the OVN SB has the
+        "Chassis_Private" table. Otherwise, is not possible to find out which
+        register is newer and thus must be kept in the database.
+        """
+        if not self._sb_idl.is_table_present('Chassis_Private'):
+            raise periodics.NeverAgain()
+
+        if not self.has_lock:
+            return
+
+        # dup_chassis_port_host = {host_name: [(ch1, ch_private1),
+        #                                      (ch2, ch_private2), ... ]}
+        dup_chassis_port_host = {}
+        chassis = self._sb_idl.chassis_list().execute(check_error=True)
+        chassis_hostnames = {ch.hostname for ch in chassis}
+        # Find the duplicated "Chassis" and "Chassis_Private" registers,
+        # comparing the hostname.
+        for hostname in chassis_hostnames:
+            ch_list = []
+            # Find these chassis matching the hostname and create a list.
+            for ch in (ch for ch in chassis if ch.hostname == hostname):
+                ch_private = self._sb_idl.lookup('Chassis_Private', ch.name,
+                                                 default=None)
+                if ch_private:
+                    ch_list.append((ch, ch_private))
+
+            # If the chassis list > 1, then we have duplicated chassis.
+            if len(ch_list) > 1:
+                # Order ch_list by Chassis_Private.nb_cfg_timestamp, from newer
+                # (greater value) to older.
+                ch_list.sort(key=lambda x: x[1].nb_cfg_timestamp, reverse=True)
+                dup_chassis_port_host[hostname] = ch_list
+
+        if not dup_chassis_port_host:
+            return
+
+        # Remove the "Chassis" and "Chassis_Private" registers with the
+        # older Chassis_Private.nb_cfg_timestamp.
+        with self._sb_idl.transaction(check_error=True) as txn:
+            for ch_list in dup_chassis_port_host.values():
+                # The first item is skipped, this is the newest element.
+                for ch, ch_private in ch_list[1:]:
+                    for table in ('Chassis_Private', 'Chassis'):
+                        txn.add(self._sb_idl.db_destroy(table, ch.name))
+
 
 class HashRingHealthCheckPeriodics(object):
 
diff --git a/neutron/tests/functional/plugins/ml2/drivers/ovn/mech_driver/ovsdb/test_maintenance.py b/neutron/tests/functional/plugins/ml2/drivers/ovn/mech_driver/ovsdb/test_maintenance.py
index 256e47a5c06..c4a8e226cf3 100644
--- a/neutron/tests/functional/plugins/ml2/drivers/ovn/mech_driver/ovsdb/test_maintenance.py
+++ b/neutron/tests/functional/plugins/ml2/drivers/ovn/mech_driver/ovsdb/test_maintenance.py
@@ -972,6 +972,64 @@ class TestMaintenance(_TestMaintenanceHelper):
         lsp = self.nb_api.lookup('Logical_Switch_Port', p1['id'])
         self.assertEqual(hcg_uuid, lsp.ha_chassis_group[0].uuid)
 
+    def test_remove_duplicated_chassis_registers(self):
+        hostnames = ['host1', 'host2']
+        for hostname in hostnames:
+            for _ in range(3):
+                self.add_fake_chassis(hostname)
+
+        chassis = self.sb_api.chassis_list().execute(check_error=True)
+        self.assertEqual(6, len(chassis))
+        # Make the chassis private timestamp different
+        for idx, ch in enumerate(chassis):
+            self.sb_api.db_set('Chassis_Private', ch.name,
+                               ('nb_cfg_timestamp', idx)).execute()
+
+        ch_private_dict = {}  # host: [ch_private1, ch_private2, ...]
+        for hostname in hostnames:
+            ch_private_list = []
+            for ch in (ch for ch in chassis if ch.hostname == hostname):
+                ch_private = self.sb_api.lookup('Chassis_Private', ch.name,
+                                                default=None)
+                if ch_private:
+                    # One of the "Chassis_Private" has been deleted on purpose
+                    # in this test.
+                    ch_private_list.append(ch_private)
+            ch_private_list.sort(key=lambda x: x.nb_cfg_timestamp,
+                                 reverse=True)
+            ch_private_dict[hostname] = ch_private_list
+
+        self.maint.remove_duplicated_chassis_registers()
+        chassis_result = self.sb_api.chassis_list().execute(check_error=True)
+        self.assertEqual(2, len(chassis_result))
+        for ch in chassis_result:
+            self.assertIn(ch.hostname, hostnames)
+            hostnames.remove(ch.hostname)
+            # From ch_private_dict[ch.hostname], we retrieve the first
+            # "Chassis_Private" register because these are ordered by
+            # timestamp. The newer one (bigger timestamp) should remain in the
+            # system.
+            ch_expected = ch_private_dict[ch.hostname][0].chassis[0]
+            self.assertEqual(ch_expected.name, ch.name)
+
+    def test_remove_duplicated_chassis_registers_no_ch_private_register(self):
+        for _ in range(2):
+            self.add_fake_chassis('host1')
+
+        chassis = self.sb_api.chassis_list().execute(check_error=True)
+        self.assertEqual(2, len(chassis))
+        # Make the chassis private timestamp different
+        # Delete on of the "Chassis_Private" registers.
+        self.sb_api.db_destroy('Chassis_Private', chassis[0].name).execute()
+        self.sb_api.db_set('Chassis_Private', chassis[1].name,
+                           ('nb_cfg_timestamp', 1)).execute()
+
+        self.maint.remove_duplicated_chassis_registers()
+        chassis_result = self.sb_api.chassis_list().execute(check_error=True)
+        # Both "Chassis" registers are still in the DB because one
+        # "Chassis_Private" register was missing.
+        self.assertEqual(2, len(chassis_result))
+
 
 class TestLogMaintenance(_TestMaintenanceHelper,
                          test_log_driver.LogApiTestCaseBase):
diff --git a/releasenotes/notes/remove_duplicated_ovn_chassis-df12fb6233ea3d3e.yaml b/releasenotes/notes/remove_duplicated_ovn_chassis-df12fb6233ea3d3e.yaml
new file mode 100644
index 00000000000..cf021363d4a
--- /dev/null
+++ b/releasenotes/notes/remove_duplicated_ovn_chassis-df12fb6233ea3d3e.yaml
@@ -0,0 +1,17 @@
+---
+issues:
+  - |
+    When using ML2/OVN, during an upgrade procedure, the OVS system-id stored
+    value can be changed. The ovn-controller service will create the "Chassis"
+    and "Chassis_Private" registers based on this OVS system-id. If the
+    ovn-controller process is not gracefully stopped, that could lead to the
+    existence of duplicated "Chassis" and "Chassis_Private" registers in the
+    OVN Southbound database.
+fixes:
+  - |
+    A new OVN maintenance method ``remove_duplicated_chassis_registers`` is
+    added. This method will periodically check the OVN Southbound "Chassis"
+    and "Chassis_Private" tables looking for duplicated registers. The older
+    ones (based on the "Chassis_Private.nb_cfg_timestamp" value) will be
+    removed when more than one register has the same hostname, that should
+    be unique.