William St Clair (died c. 1554) was a Scottish noble and the 13th Baron of Roslin.

In 1533, James V of Scotland gave him a charter renewing some of the older ones that had been granted to his ancestor, Henry I Sinclair, Earl of Orkney.

[2][1] He executed an entail of Roslin and Herbertshire to his sons William, Gilbert, Patrick, Alexander, John, Oliver, Mathew and Edward successively, upon whom failing to his brothers Oliver, Alexander, Arthur and James.

[1][3] William St Clair, Baron of Roslin received an annual pension of 300 merks from Mary of Guise for his allegiance to the Crown.

[4] He was in high favor with James V of Scotland who by his special writ of summons frequently called him to sit in Parliament.