William St Clair (died circa 1379) was a Scottish noble and by tradition the 8th Baron of Roslin.

[1] He was in minority at the time of the death of his father and grandfather and he was recorded in the Exchequer Rolls of Scotland dated 8 August 1348.

An annuity of 40 merks that had been granted to his grandfather Henry was confirmed to William St Clair by David II of Scotland at Perth on 17 September 1358.

[4] He also received a charter from King David that was dated 11 February 1358 and confirmed in 1363 for the lands of Merton and Merchamyston.

[5] 19th century historian Roland Saint-Clair quotes several charters as evidence to show that William St Clair returned safely from the Continent.