Being and Nothingness: A Phenomenological Essay on Ontology (1943) is a philosophical treatise by Jean-Paul Sartre that is regarded as the beginning of the growth of existentialism in the 20th century. The original title, in French, was L'Etre et le Néant.

The first English translation of Sartre's work was written by Ohio State University professor Hazel Barnes , in 1956.