Sir James Thynne (1605 – 12 October 1670) was an English landowner and politician who sat in the House of Commons in two periods between 1640 and 1670.
His parents' marriage and his legitimacy were the basis of a long legal dispute.
Sir Christopher Wren advised him on improvements to the house at Longleat which included the great stairs and stone terrace.
[5] In 1664 he was re-elected MP for Wiltshire in the Cavalier Parliament and sat until his death in 1670.
He died without issue and his nephew Thomas succeeded to the estates.