diff --git a/keystone/resource/core.py b/keystone/resource/core.py
index 0c2397a2f7..02fea5262c 100644
--- a/keystone/resource/core.py
+++ b/keystone/resource/core.py
@@ -37,7 +37,7 @@ MEMOIZE = cache.get_memoization_decorator(group='resource')
 
 @dependency.provider('resource_api')
 @dependency.requires('assignment_api', 'credential_api', 'domain_config_api',
-                     'identity_api', 'revoke_api')
+                     'identity_api', 'revoke_api', 'trust_api')
 class Manager(manager.Manager):
     """Default pivot point for the Resource backend.
 
@@ -467,6 +467,7 @@ class Manager(manager.Manager):
             # the specified project
             assignment.COMPUTED_ASSIGNMENTS_REGION.invalidate()
             self.credential_api.delete_credentials_for_project(project_id)
+            self.trust_api.delete_trusts_for_project(project_id)
         finally:
             # attempt to send audit event even if the cache invalidation raises
             notifications.Audit.deleted(self._PROJECT, project_id, initiator)
diff --git a/keystone/tests/unit/test_v3_trust.py b/keystone/tests/unit/test_v3_trust.py
index 77a663c13d..02b259db72 100644
--- a/keystone/tests/unit/test_v3_trust.py
+++ b/keystone/tests/unit/test_v3_trust.py
@@ -508,3 +508,30 @@ class TestTrustOperations(test_v3.RestfulTestCase):
         self.assertRaises(exception.TrustNotFound,
                           self.trust_api.get_trust,
                           trust['id'])
+
+    def test_trust_deleted_when_project_deleted(self):
+        # create trust
+        ref = unit.new_trust_ref(
+            trustor_user_id=self.user_id,
+            trustee_user_id=self.trustee_user_id,
+            project_id=self.project_id,
+            impersonation=False,
+            role_ids=[self.role_id],
+            allow_redelegation=True)
+        resp = self.post('/OS-TRUST/trusts', body={'trust': ref})
+
+        trust = self.assertValidTrustResponse(resp)
+
+        # list all trusts
+        r = self.get('/OS-TRUST/trusts')
+        self.assertEqual(1, len(r.result['trusts']))
+
+        # delete the project will delete the trust.
+        self.delete(
+            '/projects/%(project_id)s' % {'project_id': trust['project_id']})
+
+        # call the backend method directly to bypass authentication since the
+        # user no longer has the assignment on the project.
+        self.assertRaises(exception.TrustNotFound,
+                          self.trust_api.get_trust,
+                          trust['id'])
diff --git a/keystone/trust/backends/base.py b/keystone/trust/backends/base.py
index 5ebfab1904..4e11979253 100644
--- a/keystone/trust/backends/base.py
+++ b/keystone/trust/backends/base.py
@@ -70,3 +70,12 @@ class TrustDriverBase(object):
         :raises keystone.exception.TrustNotFound: If the trust doesn't exist.
         """
         raise exception.NotImplemented()  # pragma: no cover
+
+    @abc.abstractmethod
+    def delete_trusts_for_project(self, project_id):
+        """Delete all trusts for a project.
+
+        :param project_id: ID of a project to filter trusts by.
+
+        """
+        raise exception.NotImplemented()  # pragma: no cover
diff --git a/keystone/trust/backends/sql.py b/keystone/trust/backends/sql.py
index 9cdbd076d3..378fa57769 100644
--- a/keystone/trust/backends/sql.py
+++ b/keystone/trust/backends/sql.py
@@ -176,3 +176,10 @@ class Trust(base.TrustDriverBase):
             if not trust_ref:
                 raise exception.TrustNotFound(trust_id=trust_id)
             trust_ref.deleted_at = timeutils.utcnow()
+
+    def delete_trusts_for_project(self, project_id):
+        with sql.session_for_write() as session:
+            query = session.query(TrustModel)
+            trusts = query.filter_by(project_id=project_id)
+            for trust_ref in trusts:
+                trust_ref.deleted_at = timeutils.utcnow()
diff --git a/releasenotes/notes/bug-1622310-c501cf77437fdfa6.yaml b/releasenotes/notes/bug-1622310-c501cf77437fdfa6.yaml
new file mode 100644
index 0000000000..c5318a33a5
--- /dev/null
+++ b/releasenotes/notes/bug-1622310-c501cf77437fdfa6.yaml
@@ -0,0 +1,10 @@
+---
+fixes:
+  - >
+    [`bug 1622310 <https://bugs.launchpad.net/keystone/+bug/1622310>`_]
+    Keystone trust will be invalidated if the project to which the trust
+    is scoped, or the user (trustor or trustee) for which the delegation
+    is assigned, have been deleted.
+other:
+  - Abstract method ``delete_trusts_for_project`` should be implemented by
+    custom drivers.