Henry FitzRoy, 1st Duke of Grafton (1663 - 1690) was the natural son of King Charles II by Barbara Villiers, Countess of Castlemaine and later Duchess of Cleveland.

In August 1672 he was married to Isabella, the daughter and heiress of Henry Bennet, 1st Earl of Arlington, and was created Baron Sudbury , Viscount Ipswich, and Earl of Euston; in 1675 he was created Duke of Grafton. Charles II made him a Knight of the Garter in 1680. He was made a colonel of the Grenadier Guards in 1681.

He was brought up as a sailor, and saw military service at the siege of Luxembourg in 1684. At King James II's coronation he was Lord High Constable. In the rebellion of the Duke of Monmouth he commanded the royal troops in Somerset; but later he acted with John Churchill, and joined William of Orange to overthrow the King in 1688.

He died of a wound received at the storming of Cork, while leading William's forces.