Long Day's Journey into Night is a play in four acts written by American playwright Eugene O'Neill in 1939–1941 and first published posthumously in 1956. It is widely regarded as his magnum opus and one of the great American plays of the 20th century. It premiered in Sweden in February 1956 and then opened on Broadway in November 1956, winning the Tony Award for Best Play. O'Neill received the 1957 Pulitzer Prize for Drama posthumously for Long Day's Journey into Night. The work is openly autobiographical in nature. The "long day" in the title refers to the setting of the play, which takes place during one day. A Moon for the Misbegotten is a sequel to the play. Source: Wikipedia (en)