diff --git a/changelog.d/5252.feature b/changelog.d/5252.feature
new file mode 100644
index 000000000..44115b038
--- /dev/null
+++ b/changelog.d/5252.feature
@@ -0,0 +1 @@
+Add monthly active users to phonehome stats.
diff --git a/synapse/app/homeserver.py b/synapse/app/homeserver.py
index df524a23d..811b547dd 100755
--- a/synapse/app/homeserver.py
+++ b/synapse/app/homeserver.py
@@ -541,6 +541,7 @@ def run(hs):
         stats["total_room_count"] = room_count
 
         stats["daily_active_users"] = yield hs.get_datastore().count_daily_users()
+        stats["monthly_active_users"] = yield hs.get_datastore().count_monthly_users()
         stats["daily_active_rooms"] = yield hs.get_datastore().count_daily_active_rooms()
         stats["daily_messages"] = yield hs.get_datastore().count_daily_messages()
 
diff --git a/synapse/storage/__init__.py b/synapse/storage/__init__.py
index 71316f7d0..0ca6f6121 100644
--- a/synapse/storage/__init__.py
+++ b/synapse/storage/__init__.py
@@ -279,23 +279,37 @@ class DataStore(
         """
         Counts the number of users who used this homeserver in the last 24 hours.
         """
+        yesterday = int(self._clock.time_msec()) - (1000 * 60 * 60 * 24)
+        return self.runInteraction("count_daily_users", self._count_users, yesterday,)
 
-        def _count_users(txn):
-            yesterday = int(self._clock.time_msec()) - (1000 * 60 * 60 * 24)
+    def count_monthly_users(self):
+        """
+        Counts the number of users who used this homeserver in the last 30 days.
+        Note this method is intended for phonehome metrics only and is different
+        from the mau figure in synapse.storage.monthly_active_users which,
+        amongst other things, includes a 3 day grace period before a user counts.
+        """
+        thirty_days_ago = int(self._clock.time_msec()) - (1000 * 60 * 60 * 24 * 30)
+        return self.runInteraction(
+            "count_monthly_users",
+            self._count_users,
+            thirty_days_ago,
+        )
 
-            sql = """
-                SELECT COALESCE(count(*), 0) FROM (
-                    SELECT user_id FROM user_ips
-                    WHERE last_seen > ?
-                    GROUP BY user_id
-                ) u
-            """
-
-            txn.execute(sql, (yesterday,))
-            count, = txn.fetchone()
-            return count
-
-        return self.runInteraction("count_users", _count_users)
+    def _count_users(self, txn, time_from):
+        """
+        Returns number of users seen in the past time_from period
+        """
+        sql = """
+            SELECT COALESCE(count(*), 0) FROM (
+                SELECT user_id FROM user_ips
+                WHERE last_seen > ?
+                GROUP BY user_id
+            ) u
+        """
+        txn.execute(sql, (time_from,))
+        count, = txn.fetchone()
+        return count
 
     def count_r30_users(self):
         """