Oliver St Clair (died 1523) was a Scottish noble and the 12th Baron of Roslin.

He was the eldest son of the second marriage of William Sinclair, 1st Earl of Caithness, 2nd Lord Sinclair and 11th Baron of Roslin to Marjory Sutherland, daughter of Sutherland of Duffus.

However, Oliver St Clair later gave to his brother, William Sinclair, 3rd Lord Sinclair who was also known as "of Newburgh", the lands of Cousland, Dysart and Ravenscraig with the castles in return for William and his son Henry renouncing their claims to the Barony of Roslin.

[1][4] Oliver St Clair entered into a feud with Lord Borthwick which lasted for several years after St Clair threw one of the Borthwicks over the drawbridge at Roslin Castle after dinner.

[1] Oliver St Clair completed the construction of Rosslyn Chapel, which had been started by his father.