diff --git a/synapse/appservice/__init__.py b/synapse/appservice/__init__.py
index b98900731..d5a7a5ce2 100644
--- a/synapse/appservice/__init__.py
+++ b/synapse/appservice/__init__.py
@@ -14,6 +14,7 @@
 # limitations under the License.
 from synapse.api.constants import EventTypes
 from synapse.util.caches.descriptors import cachedInlineCallbacks
+from synapse.types import GroupID, get_domain_from_id
 
 from twisted.internet import defer
 
@@ -81,12 +82,13 @@ class ApplicationService(object):
     # values.
     NS_LIST = [NS_USERS, NS_ALIASES, NS_ROOMS]
 
-    def __init__(self, token, url=None, namespaces=None, hs_token=None,
+    def __init__(self, token, hostname, url=None, namespaces=None, hs_token=None,
                  sender=None, id=None, protocols=None, rate_limited=True):
         self.token = token
         self.url = url
         self.hs_token = hs_token
         self.sender = sender
+        self.server_name = hostname
         self.namespaces = self._check_namespaces(namespaces)
         self.id = id
 
@@ -125,6 +127,24 @@ class ApplicationService(object):
                     raise ValueError(
                         "Expected bool for 'exclusive' in ns '%s'" % ns
                     )
+                group_id = regex_obj.get("group_id")
+                if group_id:
+                    if not isinstance(group_id, str):
+                        raise ValueError(
+                            "Expected string for 'group_id' in ns '%s'" % ns
+                        )
+                    try:
+                        GroupID.from_string(group_id)
+                    except Exception:
+                        raise ValueError(
+                            "Expected valid group ID for 'group_id' in ns '%s'" % ns
+                        )
+
+                    if get_domain_from_id(group_id) != self.server_name:
+                        raise ValueError(
+                            "Expected 'group_id' to be this host in ns '%s'" % ns
+                        )
+
                 regex = regex_obj.get("regex")
                 if isinstance(regex, basestring):
                     regex_obj["regex"] = re.compile(regex)  # Pre-compile regex
@@ -251,6 +271,21 @@ class ApplicationService(object):
             if regex_obj["exclusive"]
         ]
 
+    def get_groups_for_user(self, user_id):
+        """Get the groups that this user is associated with by this AS
+
+        Args:
+            user_id (str): The ID of the user.
+
+        Returns:
+            iterable[str]: an iterable that yields group_id strings.
+        """
+        return (
+            regex_obj["group_id"]
+            for regex_obj in self.namespaces[ApplicationService.NS_USERS]
+            if "group_id" in regex_obj and regex_obj["regex"].match(user_id)
+        )
+
     def is_rate_limited(self):
         return self.rate_limited
 
diff --git a/synapse/config/appservice.py b/synapse/config/appservice.py
index 82c50b824..aba0aec6e 100644
--- a/synapse/config/appservice.py
+++ b/synapse/config/appservice.py
@@ -154,6 +154,7 @@ def _load_appservice(hostname, as_info, config_filename):
         )
     return ApplicationService(
         token=as_info["as_token"],
+        hostname=hostname,
         url=as_info["url"],
         namespaces=as_info["namespaces"],
         hs_token=as_info["hs_token"],
diff --git a/synapse/handlers/groups_local.py b/synapse/handlers/groups_local.py
index da00aeb0f..7e5d3f148 100644
--- a/synapse/handlers/groups_local.py
+++ b/synapse/handlers/groups_local.py
@@ -375,6 +375,12 @@ class GroupsLocalHandler(object):
     def get_publicised_groups_for_user(self, user_id):
         if self.hs.is_mine_id(user_id):
             result = yield self.store.get_publicised_groups_for_user(user_id)
+
+            # Check AS associated groups for this user - this depends on the
+            # RegExps in the AS registration file (under `users`)
+            for app_service in self.store.get_app_services():
+                result.extend(app_service.get_groups_for_user(user_id))
+
             defer.returnValue({"groups": result})
         else:
             result = yield self.transport_client.get_publicised_groups_for_user(
@@ -415,4 +421,9 @@ class GroupsLocalHandler(object):
                 uid
             )
 
+            # Check AS associated groups for this user - this depends on the
+            # RegExps in the AS registration file (under `users`)
+            for app_service in self.store.get_app_services():
+                results[uid].extend(app_service.get_groups_for_user(uid))
+
         defer.returnValue({"users": results})
diff --git a/tests/appservice/test_appservice.py b/tests/appservice/test_appservice.py
index 7586ea905..5b2b95860 100644
--- a/tests/appservice/test_appservice.py
+++ b/tests/appservice/test_appservice.py
@@ -36,6 +36,7 @@ class ApplicationServiceTestCase(unittest.TestCase):
             id="unique_identifier",
             url="some_url",
             token="some_token",
+            hostname="matrix.org",  # only used by get_groups_for_user
             namespaces={
                 ApplicationService.NS_USERS: [],
                 ApplicationService.NS_ROOMS: [],