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.

[1] 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.

Chatham and Elizabeth Grenville, her sister-in-law, are the only two women in British history to have been both the wife of a prime minister and the mother of another prime minister.

[1] At 34, Lady Hester married Whig politician William Pitt on 16 November 1754 at her home in Argyle Street, London, by Francis Ayscough under special licence.

[1][2] They had five children: On 4 December 1761, she was created "Baroness Chatham", of Chatham, in the County of Kent", with remainder to her sons by William Pitt.