favourite of Queen Anne of England. That she turned against both her patrons—Sarah Jennings, Duchess of Marlborough, and Robert Harley, Earl of Oxford—has led historians to speak harshly of her, but Jonathan Swift, who knew her intimately, spoke highly of her character and abilities.

She was the daughter of Francis Hill, a Levant merchant, who was ruined by speculation; he left four children, for whom their cousin Lady Churchill (the future Duchess of Marlborough (Marlborough, Sarah Jennings, Duchess of)) sought to provide. Through her influence Abigail Hill entered the household of Queen Anne and began, by compliant temper and Tory views, to supplant the Duchess of Marlborough in the queen's affection. In June 1707 the Duke of Marlborough suspected her of using her influence with the queen in order to further the political ends of her cousin Robert Harley (Oxford, Robert Harley, 1st Earl of, Earl Mortimer, Baron Harley of Wigmore). Already Abigail Hill had been married secretly in the queen's presence to Samuel Masham (1679?–1758), a groom of the bedchamber to Anne's consort, Prince George of Denmark. Gradually an irreparable breach developed between the duchess and Mrs. Masham. After Harley fell from office (February 1708), he contrived to negotiate with the queen through Mrs. Masham, and in 1710 he arranged through her for the queen to dismiss her ministers. Mrs. Masham succeeded to the charge of the privy purse; her brother Jack became colonel, and her husband was among the 12 Tory peers created in 1712 to secure approval of the Treaty of Utrecht. (Her husband's title was Baron Masham of Otes.)

Soon, however, Lady Masham quarreled with Oxford and set herself to foster by all the means in her power the queen's growing personal distaste for her minister. Oxford's vacillation between the Jacobites and the adherents of the Hanoverian succession to the crown probably strengthened the opposition of Lady Masham, who now warmly favoured the Jacobite party led by Viscount Bolingbroke and Francis Atterbury. Altercations took place in the queen's presence between Lady Masham and the minister; and finally, on July 27, 1714, Anne dismissed Oxford from his office of lord high treasurer and, three days later, gave the post to the Duke of Shrewsbury. Anne died on August 1, and Lady Masham then retired to private life.