Henrietta Harley, Countess of Oxford and Countess Mortimer was an English noblewoman, the only child and heiress of John Holles, 1st Duke of Newcastle and his wife, the former Lady Margaret Cavendish, daughter of Henry Cavendish, 2nd Duke of Newcastle-upon-Tyne.
Career
They had two children. Their son, Henry Cavendish Harley, Lord Harley, lived only four days.