diff --git a/example-config.yaml b/example-config.yaml
index e3aaa16b..627f923d 100644
--- a/example-config.yaml
+++ b/example-config.yaml
@@ -98,6 +98,8 @@ bridge:
     # Only enable this if your displayname_template has some static part that the bridge can use to
     # reliably identify what is a plaintext highlight.
     plaintext_highlights: false
+    # Whether or not to make portals of publicly joinable channels/supergroups publicly joinable on Matrix.
+    public_portals: true
 
     # The prefix for commands. Only required in non-management rooms.
     command_prefix: "!tg"
diff --git a/mautrix_telegram/config.py b/mautrix_telegram/config.py
index cd645e24..55b4ad46 100644
--- a/mautrix_telegram/config.py
+++ b/mautrix_telegram/config.py
@@ -175,6 +175,7 @@ class Config(DictWithRecursion):
         copy("bridge.allow_matrix_login")
         copy("bridge.inline_images")
         copy("bridge.plaintext_highlights")
+        copy("bridge.public_portals")
 
         copy("bridge.command_prefix")
 
diff --git a/mautrix_telegram/portal.py b/mautrix_telegram/portal.py
index 8a64207c..dc83f7f4 100644
--- a/mautrix_telegram/portal.py
+++ b/mautrix_telegram/portal.py
@@ -244,7 +244,7 @@ class Portal:
         self._main_intent = puppet.intent if direct else self.az.intent
 
         if self.peer_type == "channel" and entity.username:
-            public = True
+            public = config["bridge.public_portals"]
             alias = self._get_alias_localpart(entity.username)
             self.username = entity.username
         else:
@@ -403,7 +403,8 @@ class Portal:
             self.username = username or None
             if self.username:
                 await self.main_intent.add_room_alias(self.mxid, self._get_alias_localpart())
-                await self.main_intent.set_join_rule(self.mxid, "public")
+                if config["bridge.public_portals"]:
+                    await self.main_intent.set_join_rule(self.mxid, "public")
             else:
                 await self.main_intent.set_join_rule(self.mxid, "invite")