diff --git a/DOCS/man/vf.rst b/DOCS/man/vf.rst
index 86f6b8ff67..3e3a251754 100644
--- a/DOCS/man/vf.rst
+++ b/DOCS/man/vf.rst
@@ -433,7 +433,7 @@ Available mpv-only filters are:
             subtitle colors and video under the influence of the video equalizer
             settings.
 
-``vapoursynth=file:buffered-frames:concurrent-frames``
+``vapoursynth=file:buffered-frames:concurrent-frames:user-data``
     Loads a VapourSynth filter script. This is intended for streamed
     processing: mpv actually provides a source filter, instead of using a
     native VapourSynth video source. The mpv source will answer frame
@@ -559,6 +559,10 @@ Available mpv-only filters are:
         By default, this uses the special value ``auto``, which sets the option
         to the number of detected logical CPU cores.
 
+    ``user-data``
+        Optional arbitrary string that is passed to the script. Default to empty
+        string if not set.
+
     The following ``.vpy`` script variables are defined by mpv:
 
     ``video_in``
@@ -589,6 +593,10 @@ Available mpv-only filters are:
         to the height. These values can be 0. Note that this will not respond to
         monitor changes and may not work on all platforms.
 
+    ``user_data``
+        User data passed from the filter. This variable always exists, and defaults
+        to empty string.
+
 ``vavpp``
     VA-API video post processing. Requires the system to support VA-API,
     i.e. Linux/BSD only. Works with ``--vo=vaapi`` and ``--vo=gpu`` only.
diff --git a/video/filter/vf_vapoursynth.c b/video/filter/vf_vapoursynth.c
index 597ef5cbf2..5446fc5ce5 100644
--- a/video/filter/vf_vapoursynth.c
+++ b/video/filter/vf_vapoursynth.c
@@ -46,6 +46,7 @@ struct vapoursynth_opts {
     char *file;
     int maxbuffer;
     int maxrequests;
+    char *user_data;
 
     const struct script_driver *drv;
 };
@@ -699,6 +700,7 @@ static int reinit_vs(struct priv *p, struct mp_image *input)
     p->vsapi->propSetFloat(vars, "container_fps", container_fps, 0);
     p->vsapi->propSetFloat(vars, "display_fps", display_fps, 0);
     p->vsapi->propSetIntArray(vars, "display_res", display_res, 2);
+    p->vsapi->propSetData(vars, "user_data", p->opts->user_data, -1, 0);
 
     if (p->drv->load(p, vars) < 0)
         goto error;
@@ -830,6 +832,7 @@ static const m_option_t vf_opts_fields[] = {
         OPTDEF_INT(4)},
     {"concurrent-frames", OPT_CHOICE(maxrequests, {"auto", -1}),
         M_RANGE(1, 99), OPTDEF_INT(-1)},
+    {"user-data", OPT_STRING(user_data), OPTDEF_STR("")},
     {0}
 };