An elongated and rocky summit on a ridge which links Beinn Narnain and A' Chrois in E Argyll and Bute, Creag Tharsuinn rises steeply to 781m (2562 feet) 2½ miles (4 km) northwest of Arrochar. There are several subsidiary summits on both sides of the principal peak. The Sugach Buttress lies within a corrie immediately to the southeast which is the source of Allt Sugach.