Gwaun y Llwyni is a subsidiary summit of Aran Fawddwy in southern Snowdonia, Wales.

It forms a part of the Aran mountain range.

The peak's southern face is very steep and forms one of the backwalls of Cwm Cywarch.

The summit is grassy and is marked by a small cairn.

Pen yr Allt Uchaf rises on the other side of Cwm Cywarch, Aran Fawddwy is to the north-east, Waun Camddwr to the north and Glasgwm to the west.