diff --git a/synapse/config/server.py b/synapse/config/server.py
index 1b8968608..2913f64dd 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -178,6 +178,12 @@ class ServerConfig(Config):
         # events with profile information that differ from the target's global profile.
         self.allow_per_room_profiles = config.get("allow_per_room_profiles", True)
 
+        # Whether to show the users on this homeserver in the user directory. Defaults to
+        # True.
+        self.show_users_in_user_directory = config.get(
+            "show_users_in_user_directory", True,
+        )
+
         self.listeners = []
         for listener in config.get("listeners", []):
             if not isinstance(listener.get("port", None), int):
@@ -577,6 +583,11 @@ class ServerConfig(Config):
         # Defaults to 'true'.
         #
         #allow_per_room_profiles: false
+
+        # Whether to show the users on this homeserver in the user directory. Defaults to
+        # 'true'.
+        #
+        #show_users_in_user_directory: false
         """ % locals()
 
     def read_arguments(self, args):
diff --git a/synapse/handlers/register.py b/synapse/handlers/register.py
index 68d87163a..bd8f522fa 100644
--- a/synapse/handlers/register.py
+++ b/synapse/handlers/register.py
@@ -74,6 +74,8 @@ class RegistrationHandler(BaseHandler):
         )
         self._server_notices_mxid = hs.config.server_notices_mxid
 
+        self._show_in_user_directory = self.hs.show_users_in_user_directory
+
         if hs.config.worker_app:
             self._register_client = ReplicationRegisterServlet.make_client(hs)
             self._register_device_client = (
@@ -289,6 +291,14 @@ class RegistrationHandler(BaseHandler):
                 user_id, threepid_dict, None, False,
             )
 
+        # Prevent the new user from showing up in the user directory if the server
+        # mandates it.
+        if self._show_in_user_directory:
+            yield self.store.add_account_data_for_user(
+                user_id, "im.vector.hide_profile", {'hide_profile': True},
+            )
+            yield self.profile_handler.set_active(user, False, True)
+
         defer.returnValue((user_id, token))
 
     @defer.inlineCallbacks