HMS Mordaunt was a 46-gun ship of the line of the Royal Navy, launched at Deptford in 1681 and in active service during the Nine Years' War with France.

Plans for the vessel's construction were developed in the late 1670s by a private syndicate headed by Charles Mordaunt, 3rd Earl of Peterborough, with the publicised intention that she be used solely as a merchantman.

A contract for her construction was issued in 1680 to William Castle, a commercial shipwright at Deptford, initially on behalf of the syndicate and then solely in the name of Charles Mordaunt.

The vessel's stern featured a carved crest displaying the Mordaunt family coat of arms: a chevron beneath three stars.

In early 1681 Spain's Ambassador to England wrote to Admiralty expressing his fear that the vessel would be sold to the Elector of Brandenburg, who was assembling a fleet to prey on Spanish shipping.

Charles Mordaunt appeared before the court in July to attest that the vessel was indeed a merchantman, and that the heavy armament was simply to enable her to sail without convoy protection.

[1] Her crew were offered a transfer into naval service to accompany their ship, and most agreed; the civil claim was settled in their favour in May 1683 but the outstanding wages were never subsequently paid.

In 1685 she returned to Britain and was involved in the suppression of the Argyll Uprising later that year, in which she must have captured the Sophia, as her crew were awarded a share of the £5000 prize paid by the English government in August 1685.