Hester Pitt, Countess of Chatham (née Grenville; 8 November 1720 – 9 April 1803) was the wife of William Pitt the Elder, 1st Earl of Chatham, who was prime minister of Great Britain from 1766 to 1768. The sister of George Grenville, who was prime minister from 1763 to 1765, she was also the mother of Prime Minister William Pitt the Younger and a niece of the noted Whig politician Richard Temple, 1st Viscount Cobham, who had served as her husband's mentor.