John Sinclair, Lord Herdmanston, (14 February 1632 – 13 July 1666) was a Scottish noble of the 17th century.
Through his brother Matthew, he was uncle to Charles St Clair of Herdmanston, later de jure Lord Sinclair (grandfather to Charles St Clair, 13th Lord Sinclair),[2] and Dr. Andrew St Clair, physician to King George II.
[1] St Clair was taken prisoner at the Battle of Worcester in 1651, and exempted from Cromwell's Act of Grace.
Among their children were:[1] St Clair died on 13 July 1666 and was buried at Greyfriars Kirkyard.
Through his son Henry, he was a grandfather of John St Clair, Master of Sinclair (1683–1750), who was attainted in 1715 and never allowed to assume title, and James St Clair (d. 1762), who never assumed the title.