Sir John Thynne (21 September 1555 – 21 November 1604) of Longleat House, Wiltshire, was an English landowner and Member of Parliament. He was the eldest son of Sir John Thynne of Longleat and Christian, the daughter of Sir Richard Gresham, a London mercer and educated at Oxford University, graduating BA in 1573. He succeeded his father in 1580, inheriting Longleat House, which his father had built, and was knighted in 1603.