diff --git a/booru_viewer/gui/media/video_player.py b/booru_viewer/gui/media/video_player.py
index fb13756..8ab6eb2 100644
--- a/booru_viewer/gui/media/video_player.py
+++ b/booru_viewer/gui/media/video_player.py
@@ -337,6 +337,7 @@ class VideoPlayer(QWidget):
         self._stream_record_tmp: Path | None = None
         self._stream_record_target: Path | None = None
         self._seeked_during_record: bool = False
+        self._loudnorm: bool = False
 
     def _ensure_mpv(self) -> mpvlib.MPV:
         """Set up mpv callbacks on first use. MPV instance is pre-created."""
@@ -364,6 +365,9 @@ class VideoPlayer(QWidget):
         # exists. The qproperty-letterboxColor setter is a no-op if mpv
         # hasn't been initialized yet, so we have to (re)apply on init.
         self._apply_letterbox_color()
+        # Apply audio normalization if enabled in settings.
+        if self._loudnorm:
+            self._mpv.af = "loudnorm"
         return self._mpv
 
     # -- Public API (used by app.py for state sync) --