Thomas Wintour (also spelt Wyntour) (1571 (although some accounts say 1572) - January 31 1606), was one of the principal catholic conspirators in the 1605 Gunpowder Plot to assassinate James I of England and Members of Parliament. His brother Robert Wintour was also a prominent member of the conspiracy. He was married to Elizabeth Catesby, the sister of yet another of the leading members of the conspiracy, Robert Catesby.