Coity Mountain (also spelled Coety Mountain, Welsh: Mynydd Coety) is a flat-topped mountain in the South Wales Valleys, between Blaenavon and Abertillery. The highest points of both Torfaen and Blaenau Gwent unitary authorities are at the summit of Coity Mountain. The summit is also known as Twyn Ffynhonnau Goerion. Some 2 km (1 mi) to the southeast lies a major subsidiary top of the hill, Mynydd Varteg Fawr (549m) at the southeastern end of whose broad ridge is a trig point at 544m. A few hundred metres to the southeast of this summit is a memorial known as the "Dog Stone" which commemorates Carlo the Red Setter, a dog shot accidentally by his master while hunting on the 12 August 1864. It has an unmarked summit and is a UK listed Marilyn.