Henry Mordaunt, 2nd Earl of Peterborough KG PC FRS (15 November 1621 – 19 June 1697) was an English soldier, peer and courtier.

A private interview with Charles I as he passed through Ampthill to Hampton Court, in the summer of 1647, prompted him to make a last effort on the king's behalf, and in July 1648 he united with George Villiers, 2nd Duke of Buckingham and Henry Rich, 1st Earl of Holland in raising the royal standard at Dorking.

The plan was to seize Reigate, but foiled in this, the insurgents were driven back on Kingston, and eventually dispersed in the neighbourhood of Harrow by the parliamentary forces (7 July).

In April 1662, he concluded a treaty with the Moors under Ahmad al-Khadir ibn Ali Ghaïlan but, in a disastrous sally out (3 May 1662), his force was soundly defeated.

[3] He served in the Dutch war, at first as a volunteer in the fleet of the Earl of Sandwich, afterwards in command of the Unicorn at the Battle of Lowestoft in 1665 under James, Duke of York.

In 1670 he was appointed Groom of the Stole to the Duke of York, and on 24 February 1673 ambassador extraordinary to arrange the terms of his proposed marriage with the Archduchess Claudia Felicitas of Innsbruck.

After some demur on the grounds of religion, Pope Clement X refusing a dispensation for the marriage of the princess with a prince who was not a declared Catholic, the scruples of the family were overcome, Peterborough being proxy for the duke (30 September 1673).

Nevertheless, though suffering from fever, he had himself carried down to Westminster Hall, to vote against the condemnation of Lord Stafford (7 December) In October 1681 he was summoned to Scotland by the Duke of York, whom he attended on his return to England in the following March.

[1] He bore St. Edward's sceptre at the coronation of James II, by whom he was made Groom of the Stole and a Knight of the Garter in 1685, and colonel of the 3rd regiment of horse.