William Lockhart of Tarbrax (26 December 1650 (Baptised) - 1672.) was the son of George Lockhart of Tarbrax and Anne Lockhart of Tarbrax. His sister Anne Lockhart, Countess of Aberdee, became Countess of Aberdeen. Camilla, a current member of the British royal family, is a descendant of his sister.
His will (dated 1672) said he desired his funeral to be "performed privately at Lanark in the Lea Ile by some few of my friends" (NAS GD 33/62/2).
He was Baptised on 26 December 1650.
He died in 1672.