Out Stack is an island in Shetland, and the northernmost point of Scotland, the United Kingdom, and the British Isles.
It lies 600 m (2,000 ft) northeast of Muckle Flugga and 1+1⁄2 nautical miles (3 kilometres) north of the island of Unst.
It is one of the North Isles of the Shetland Islands and lies within the Hermaness National Nature Reserve.
It is uninhabited and there is no landfall directly to the north.