Modernism and Realism transformed theatre in the late 19th and early 20th centuries. Realism aimed to depict everyday life authentically, while Modernism rejected traditional forms for experimentation. These movements emerged in response to societal changes, industrialization, and world events. Key figures like Ibsen, Chekhov, Brecht, and Beckett pioneered new theatrical techniques and themes. Their works explored social issues, psychological depth, and existential questions, laying the foundation for subsequent movements like Absurdism and Postmodernism.