Castle Gay is a novel by John Buchan. It is the second of his three Dickson McCunn books and is set in south west Scotland in the Dumfries and Galloway region in the 1920s.

Castle Gay is one half Pilgrim’s Progress, one half commentary on tradition, mixed up in a splendid adventure story. It begins with a dull, timid newspaper magnate, Thomas Carlyle Craw, who finds himself kidnapped (victim of a misfired college prank) and deposited in a lodge in the remote Border mountains of Scotland. Irascible, whiny, and wholly unused to bodily exertion, he is forced to undertake a lengthy sojourn in the wilderness, by the end of which he has become a new man. But his is no tale of solitary man battling the impersonal forces of nature and finding strength to conquer deep within himself; from the outset, like Dante, he is given a guide through the scenes of humiliation. It is no hell through which he travels, but the comfortable and homely world of the Scots countryside, quick to offer him a bed by the fire and endless plates of ham and eggs. Yet this same world also offers dangers and discomfort aplenty, and with them comes slow life into the soul of the pilgrim.

The Dickson McCunn Trilogy is a set of three books by John Buchan. The novels in the trilogy are Huntingtower (1922), Castle Gay (1930) and The House of the Four Winds (1935).

John Buchan, 1st Baron Tweedsmuir PC GCMG GCVO CH (26 August 1875 – 11 February 1940) was a Scottish novelist, historian and Unionist politician who served as Governor General of Canada, the 15th since Canadian Confederation.

After a brief legal career Buchan simultaneously began both his writing career and his political and diplomatic career, serving as a private secretary to the colonial administrator of various colonies in Southern Africa. He eventually wrote propaganda for the British war effort in the First World War. Once he was back in civilian life Buchan was elected Member of Parliament for the Combined Scottish Universities, but he spent most of his time on his writing career, notably writing The Thirty-Nine Steps and other adventure fiction.