John Mordaunt, 1st Earl of Peterborough (died 18 June 1642) was an English peer.
He was made a ward of Archbishop George Abbot, and educated at Oxford.
By Charles I, he was created Earl of Peterborough, by letters patent of 9 March 1628.
[citation needed] On the outbreak of the First English Civil War he adhered to the parliament, and held the commission of general of the ordnance under the Earl of Essex, but he died of consumption, on 18 June 1642.
Lady Peterborough was a noted beauty but was also famed for piety: she was a close friend of James Ussher, Archbishop of Armagh, who spent his last years in her house.