Isabella FitzRoy, Duchess of Grafton

Her Grace The Duchess of Grafton, suo jure Countess of Arlington
The countess and her son
Personal details
Born	Isabella Bennet c. 1668
Died	7 February 1723
Spouse(s)	Henry FitzRoy, 1st Duke of Grafton
Children	Charles FitzRoy, 2nd Duke of Grafton
Parents	Henry Bennet, 1st Earl of Arlington Isabella de Nassau

Isabella Bennet FitzRoy, 2nd Countess of Arlington and Duchess of Grafton (c. 1668–7 February 1723) was a British peer and heiress.

Isabella was the daughter of Henry Bennet, 1st Earl of Arlington, a Royalist commander, by his wife, Isabella de Nassau (1633–1718). (Her mother was a daughter of Louis of Nassau-Beverweerd and thus a granddaughter of Maurice of Nassau, Prince of Orange, and a great-granddaughter of William the Silent). Henry was created Baron Arlington for his loyalty to the crown. Lord Arlington was later further raised in the peerage to the titles of Earl of Arlington and Viscount Thetford, all of which were created with special remainder to allow women to inherit.

Isabella was married at the age of four to Henry FitzRoy, Earl of Euston (later created Duke of Grafton), the nine-year-old illegitimate son of King Charles II. The wedding ceremony was repeated on 7 November 1679 and they lived at Euston Hall. Isabella and her husband had one son, Charles FitzRoy, 2nd Duke of Grafton, who succeeded both his parents as 2nd Duke of Grafton and 3rd Earl of Arlington. After her first husband's death in 1690 from a wound received at the storming of Cork while leading the forces of William of Orange, the Duchess of Grafton remarried on 14 October 1698 to Sir Thomas Hanmer.

On the death of her father in 1685, Isabella succeeded to his titles suo jure.

Isabella is one of the Hampton Court Beauties painted by Sir Godfrey Kneller for Queen Mary II.