Tarren y Gesail is a Hewitt of 666.9 m in Gwynedd. It is one of only four register hills in the Dolgellau to Machynlleth region, with Cadair Idris – Penygadair, Maesglase and Tarrenhendre.
On the Hewitts height ladder it sits between Muckish (667.1 m) and Knocknafallia (666.5 m). Its nearest higher summit, Mynydd Pencoed (766 m, 5.9 km north), is a listed top not profiled here.