Lewis and Harris, or Lewis with Harris, is a single Scottish island in the Outer Hebrides, divided by mountains. It is the largest island in Scotland and the third largest in the British Isles, after Great Britain and the island of Ireland, with an area of 841 square miles (2,178 km2), which is approximately 1% of the area of Great Britain. The northern two-thirds is called [the Isle of] Lewis and the southern third [the Isle of] Harris; each is referred to as if it were a separate island and there are many cultural and linguistic differences between the two.

The Outer Hebrides or Western Isles, sometimes known as the Long Isle or Long Island, is an island chain off the west coast of mainland Scotland. The islands are geographically coextensive with Comhairle nan Eilean Siar, one of the 32 unitary council areas of Scotland. They form part of the archipelago of the Hebrides, separated from the Scottish mainland and from the Inner Hebrides by the waters of the Minch, the Little Minch, and the Sea of the Hebrides.