Elizabeth Sigmund (1928–2017) was a British author, activist, and close friend of poet Sylvia Plath. Perhaps best known for her activism against chemical warfare, she was co-ordinator of the Organophosphate Information Network and was involved with the Working Party on Chemical and Biological Weapons from the mid-1960s. For this work, she was awarded an Honorary Doctorate by the University of Plymouth in 2001. Sigmund was the co-dedicatee of Plath's novel The Bell Jar. She passed away in 2017 at the age of 88.