diff --git a/ironic/conductor/rpcapi.py b/ironic/conductor/rpcapi.py
index 8b1262dc7b..1894690307 100644
--- a/ironic/conductor/rpcapi.py
+++ b/ironic/conductor/rpcapi.py
@@ -128,6 +128,10 @@ class ConductorAPI(object):
         """
         self.ring_manager.reset()
 
+        # There are no conductors, temporary failure - 503 Service Unavailable
+        if not self.ring_manager.ring:
+            raise exception.TemporaryFailure()
+
         try:
             ring = self.ring_manager[node.driver]
             dest = ring.get_nodes(node.uuid.encode('utf-8'),
diff --git a/ironic/tests/unit/conductor/test_rpcapi.py b/ironic/tests/unit/conductor/test_rpcapi.py
index 92e74313d4..d6364aa244 100644
--- a/ironic/tests/unit/conductor/test_rpcapi.py
+++ b/ironic/tests/unit/conductor/test_rpcapi.py
@@ -98,7 +98,7 @@ class RPCAPITestCase(db_base.DbTestCase):
         CONF.set_override('host', 'fake-host')
 
         rpcapi = conductor_rpcapi.ConductorAPI(topic='fake-topic')
-        self.assertRaises(exception.NoValidHost,
+        self.assertRaises(exception.TemporaryFailure,
                           rpcapi.get_topic_for,
                           self.fake_node_obj)
 
diff --git a/releasenotes/notes/story-2002600-return-503-if-no-conductors-online-ead1512628182ec4.yaml b/releasenotes/notes/story-2002600-return-503-if-no-conductors-online-ead1512628182ec4.yaml
new file mode 100644
index 0000000000..219a033112
--- /dev/null
+++ b/releasenotes/notes/story-2002600-return-503-if-no-conductors-online-ead1512628182ec4.yaml
@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Ironic API now returns ``503 Service Unavailable`` for action requiring a
+    conductor when no conductors are online.
+    `Bug: 2002600 <https://storyboard.openstack.org/#!/story/2002600>`_.