Frances Julia Percy, Duchess of Northumberland ( Burrell; 21 December 1752 – 28 April 1820) was the second wife of Hugh Percy, 2nd Duke of Northumberland, and the mother of the 3rd and 4th Dukes.
Frances was a daughter of the barrister Peter Burrell, of Beckenham, Kent, and his wife, the former Elizabeth Lewis. Her brother was Peter Burrell, 1st Baron Gwydyr, and two of her sisters also married into the aristocracy: Elizabeth, who married the Duke of Hamilton (and later the Marquess of Exeter), and Isabella, who became Countess of Beverley. Isabella's husband, Algernon Percy, was the younger brother of Frances's husband, Hugh Percy.
She married the future duke, then styled as an earl, in May 1779, shortly after his childless marriage to the former Lady Anne Crichton-Stuart had been dissolved by Act of Parliament. He inherited the dukedom when his father died in 1786, making his wife a duchess.
Their children were:
The duke died in 1817, and Frances, now dowager duchess, died in 1820, three months after her oldest surviving daughter Elizabeth died at Syon House, aged 38. Like her daughter Elizabeth and her sister Isabella, Frances was buried in the Northumberland Vault in Westminster Abbey.