Penelope Ruth Mortimer (maiden Fletcher, September 19, 1918 - October 19, 1999) was a British-born English journalist, biographer, and novelist. Her semi-autobiographical novel "The Pumpkin Eater" (1962) was adapted into a 1964 film for which Anne Bancroft was nominated for an Oscar for Best Actress for her role as Jo Armitage, a character based on Mortimer herself.

Mortimer wrote over a dozen novels during his career, focusing on upper-middle-class life in British society, he also worked as a freelance journalist, his work regularly appearing in The New Yorker. As a Daily Mail columnist, he wrote under the pseudonym Ann Temple. In the late 1960s, he replaced Penelope Gilliatt as a film critic for The Observer.

Penelope Mortimer died of cancer in Kensington, London at age 81