This article delves into Eugene O'Neill's use of intertextuality in his plays, examining how he weaves together themes from mythology, literature, religion, and psychoanalysis. It explores key works by O'Neill, including Long Day's Journey into Night (1956), The Iceman Cometh (1930), and The Mourning Becomes Electra (1921), analyzing the central themes of suffering, fate, family secrets, and psychological trauma. Through intertextual references to classical mythology, Shakespearean tragedies, and Freudian psychology, O'Neill creates deeply layered works that engage with universal human experiences. The article highlights how O'Neill’s exploration of these themes contributes to his dramatic legacy and provides insights into the psychological depth of his characters.