diff --git a/libavcodec/hevc_sei.c b/libavcodec/hevc_sei.c
index 60570690cf..173689198c 100644
--- a/libavcodec/hevc_sei.c
+++ b/libavcodec/hevc_sei.c
@@ -213,6 +213,32 @@ static int decode_registered_user_data_closed_caption(HEVCSEIA53Caption *s, GetB
     return 0;
 }
 
+static int decode_nal_sei_user_data_unregistered(HEVCSEIUnregistered *s, GetBitContext *gb,
+                                                      int size)
+{
+    AVBufferRef *buf_ref, **tmp;
+
+    if (size < 16 || size >= INT_MAX - 1)
+       return AVERROR_INVALIDDATA;
+
+    tmp = av_realloc_array(s->buf_ref, s->nb_buf_ref + 1, sizeof(*s->buf_ref));
+    if (!tmp)
+        return AVERROR(ENOMEM);
+    s->buf_ref = tmp;
+
+    buf_ref = av_buffer_alloc(size + 1);
+    if (!buf_ref)
+        return AVERROR(ENOMEM);
+
+    for (int i = 0; i < size; i++)
+        buf_ref->data[i] = get_bits(gb, 8);
+    buf_ref->data[size] = 0;
+    buf_ref->size = size;
+    s->buf_ref[s->nb_buf_ref++] = buf_ref;
+
+    return 0;
+}
+
 static int decode_nal_sei_user_data_registered_itu_t_t35(HEVCSEI *s, GetBitContext *gb,
                                                          int size)
 {
@@ -300,6 +326,8 @@ static int decode_nal_sei_prefix(GetBitContext *gb, void *logctx, HEVCSEI *s,
         return decode_nal_sei_active_parameter_sets(s, gb, logctx);
     case HEVC_SEI_TYPE_USER_DATA_REGISTERED_ITU_T_T35:
         return decode_nal_sei_user_data_registered_itu_t_t35(s, gb, size);
+    case HEVC_SEI_TYPE_USER_DATA_UNREGISTERED:
+        return decode_nal_sei_user_data_unregistered(&s->unregistered, gb, size);
     case HEVC_SEI_TYPE_ALTERNATIVE_TRANSFER_CHARACTERISTICS:
         return decode_nal_sei_alternative_transfer(&s->alternative_transfer, gb);
     default:
@@ -371,4 +399,9 @@ int ff_hevc_decode_nal_sei(GetBitContext *gb, void *logctx, HEVCSEI *s,
 void ff_hevc_reset_sei(HEVCSEI *s)
 {
     av_buffer_unref(&s->a53_caption.buf_ref);
+
+    for (int i = 0; i < s->unregistered.nb_buf_ref; i++)
+        av_buffer_unref(&s->unregistered.buf_ref[i]);
+    s->unregistered.nb_buf_ref = 0;
+    av_freep(&s->unregistered.buf_ref);
 }
diff --git a/libavcodec/hevc_sei.h b/libavcodec/hevc_sei.h
index a44ccca7f8..3618d162df 100644
--- a/libavcodec/hevc_sei.h
+++ b/libavcodec/hevc_sei.h
@@ -91,6 +91,11 @@ typedef struct HEVCSEIA53Caption {
     AVBufferRef *buf_ref;
 } HEVCSEIA53Caption;
 
+typedef struct HEVCSEIUnregistered {
+    AVBufferRef **buf_ref;
+    int nb_buf_ref;
+} HEVCSEIUnregistered;
+
 typedef struct HEVCSEIMasteringDisplay {
     int present;
     uint16_t display_primaries[3][2];
@@ -116,6 +121,7 @@ typedef struct HEVCSEI {
     HEVCSEIDisplayOrientation display_orientation;
     HEVCSEIPictureTiming picture_timing;
     HEVCSEIA53Caption a53_caption;
+    HEVCSEIUnregistered unregistered;
     HEVCSEIMasteringDisplay mastering_display;
     HEVCSEIContentLight content_light;
     int active_seq_parameter_set_id;
diff --git a/libavcodec/hevcdec.c b/libavcodec/hevcdec.c
index 0772608a30..c9e28f5826 100644
--- a/libavcodec/hevcdec.c
+++ b/libavcodec/hevcdec.c
@@ -2794,6 +2794,20 @@ static int set_side_data(HEVCContext *s)
         s->avctx->properties |= FF_CODEC_PROPERTY_CLOSED_CAPTIONS;
     }
 
+    for (int i = 0; i < s->sei.unregistered.nb_buf_ref; i++) {
+        HEVCSEIUnregistered *unreg = &s->sei.unregistered;
+
+        if (unreg->buf_ref[i]) {
+            AVFrameSideData *sd = av_frame_new_side_data_from_buf(out,
+                    AV_FRAME_DATA_SEI_UNREGISTERED,
+                    unreg->buf_ref[i]);
+            if (!sd)
+                av_buffer_unref(&unreg->buf_ref[i]);
+            unreg->buf_ref[i] = NULL;
+        }
+    }
+    s->sei.unregistered.nb_buf_ref = 0;
+
     return 0;
 }
 
diff --git a/tests/ref/fate/hevc-monochrome-crop b/tests/ref/fate/hevc-monochrome-crop
index 4e45412acf..384404da66 100644
--- a/tests/ref/fate/hevc-monochrome-crop
+++ b/tests/ref/fate/hevc-monochrome-crop
@@ -1,6 +1,9 @@
 [FRAME]
 width=384
 height=240
+[SIDE_DATA]
+side_data_type=H.26[45] User Data Unregistered SEI message
+[/SIDE_DATA]
 [/FRAME]
 [STREAM]
 width=384