Theresa Thornycroft (1853–1947) was an English sculptor and member of the Thornycroft family of artists. Her brother Sir Hamo Thornycroft RA, sisters Alyce Thornycroft and Helen Thornycroft were all artists, while her brother Sir John Isaac Thornycroft was the founder of the Thornycroft shipbuilding company. She married Alfred Ezra Sassoon of the Sassoon family, and in 1886 gave birth to Siegfried Sassoon, who would become an acclaimed poet during World War I. The couple had two other sons, Michael and Hamo, before their separation. Theresa continued to live in the village of Matfield in Kent, and was immortalised in the memoirs of her son Siegfried.