Existentialism Is a Humanism is a 1946 work by the philosopher Jean-Paul Sartre, based on a lecture by the same name he gave at Club Maintenant in Paris, on 29 October 1945. In early translations, Existentialism and Humanism was the title used in the United Kingdom; the work was originally published in the United States as Existentialism, and a later translation employs the original title.

Jean-Paul Charles Aymard Sartre was a French philosopher, playwright, novelist, screenwriter, political activist, biographer, and literary critic, considered a leading figure in 20th-century French philosophy and Marxism. Sartre was one of the key figures in the philosophy of existentialism. His work has influenced sociology, critical theory, post-colonial theory, and literary studies. He was awarded the 1964 Nobel Prize in Literature despite attempting to refuse it, saying that he always declined official honors and that "a writer should not allow himself to be turned into an institution."