Sir William Galbraith, 4th of that Ilk, Lord of Buthernock and Kincaid, was a Scottish noble. He was the eldest son of Arthur Galbraith.
William took part in the rescue of the boy king Alexander III from his father-in-law John Comyn I of Badenoch‘s control. William become one of the co-Regents of Scotland in 1255.
He is known to have married a daughter of John Comyn I of Badenoch, they are known to have had the following issue:
. Iain Moncreiffe of that Ilk. The Highland Clans. 1967. Barrie & Rocklif. London.