Soay lies some 40 miles (64 km) west-northwest of North Uist in the North Atlantic It is about 2 kilometres (1.2 mi) north-west of Hirta, from which it is separated by the narrow Sound of Soay, which is only about 500 metres wide. Two sea stacks, Stac Shoaigh (Soay Stac), 61 metres (200 ft), and Stac Biorach, 73 metres (240 ft), lie between. The island covers about 96.8 hectares (239 acres) and reaches a height of 378 metres (1,240 ft), the cliffs rising sheer from the sea.
The island is formed of a breccia of gabbro and dolerites and is a single mountain peak rising from the sea-bed, without Ice-Age erosion.
FeralSoay sheep are a relict population of the first sheep brought to northern Europe around 5000BC. They were kept for their wool, which was plucked, not shorn, and made into tweed. Only occasionally were the sheep killed for meat. When the neighbouring island of Hirta became uninhabited, Soay sheep were introduced there too, and more recently they have become widely kept elsewhere as a livestock animal. Another somewhat less primitive breed lives on another island in the group, the Boreray.