John Sheffield, Duke of Buckinghamshire

John Sheffield, 1st Duke of Buckingham and Normanby (8 September 1647 – 24 February 1721) was a British military officer, writer and Tory politician who served as Lord Privy Seal and Lord President of the Council. He was also known by his original title, Lord Mulgrave.

John Sheffield was the only son of Edmund Sheffield, 2nd Earl of Mulgrave, and succeeded his father as 3rd Earl and 5th Baron Sheffield in 1658.

At the age of eighteen he joined the fleet, to serve in the Second Anglo-Dutch War; on the renewal of hostilities in 1672 he was present at the Battle of Sole Bay, and in the next year received the command of a ship. He was also made a colonel of infantry, and served for some time under Henri de La Tour d'Auvergne, Viscount of Turenne. He was made a Knight of the Garter in 1674. In 1680 he was put in charge of an expedition sent to relieve the Garrison of the town of Tangier, which was then under siege by Moulay Ismail ibn Sharif. It was said that he was provided with a rotten ship in the hope that he would not return, but the reason of this abortive plot, if plot there was, is not exactly ascertained. At court he took the side of the Duke of York and helped to bring about the Duke of Monmouth's disgrace.