The Gaidhealtachd is the region in Scotland and Nova Scotia where Scottish Gaelic is spoken as the native language by most or some part of the population.

In the past, the Gaidhealtachd has included much of Scotland outside the extreme south east, the north east and the Northern Isles, as evidenced by the prevalence of Gaelic derived place names throughout Scotland, and contemporary accounts. These include Dundee from the Gaelic Dun Deagh, Inverness from Inbhir Nis, Stirling from Sruighlea, Argyll from Earra-Ghàidheal and Galloway from Gall-Ghaidhealaibh. In contrast Glasgow takes its name from the Brythonic glas cu (Gaelic Glaschu). Aberdeen too, comes from Brythonic roots. For historical reasons, including the influence of a Scots-speaking court in Edinburgh, the Gaidhealtachd has been reduced massively to the present region of the Western Isles, and the North West Highlands, Skye and Lochalsh and Argyll and Bute, with small Gaelic populations existing in Glasgow and Edinburgh.

Gaelic has also survived among communities descended from immigrants in parts of Nova Scotia, Prince Edward Island and Newfoundland in eastern Canada and those areas where Gaelic is spoken can also be said to be Gaidhealtachdan.

The equivalent word for an Irish Gaelic speaking area is Gaeltacht.