Eugene O'Neill was an American playwright and a Nobel laureate in Literature. His plays were among the first to introduce in American drama the techniques of realism, associated with Russian playwright Anton Chekhov, Norwegian playwright Henrik Ibsen, and Swedish playwright August Strindberg.

His plays included speeches in American vernacular and involved characters on the fringes of society, engaging in depraved behavior. They struggle to maintain their hopes and aspirations, ultimately sliding into disillusionment and despair. O'Neill wrote only one well-known comedy, Ah, Wilderness! Nearly all his other plays involve some degree of tragedy and personal pessimism.

Among his works, Long Day's Journey into Night is often included on lists of the finest U.S. plays in the 20th century, alongside A Streetcar Named Desire by Tennessee Williams and Death of a Salesman by Arthur Miller.

He won the 1936 Nobel Prize in Literature and is the only playwright to win four Pulitzer Prizes for Drama.