diff --git a/niri/config.kdl b/niri/config.kdl
index b6ce783..c8eb276 100644
--- a/niri/config.kdl
+++ b/niri/config.kdl
@@ -184,3 +184,16 @@ window-rule {
         off
     }
 }
+
+// Steam Big Picture mode: open fullscreen, borderless
+window-rule {
+    match app-id="^steam$" title="^Steam Big Picture Mode$"
+    open-fullscreen true
+    open-floating false
+    border {
+        off
+    }
+    focus-ring {
+        off
+    }
+}