Uta Thyra Hagen (12 June 1919 – 14 January 2004) was a German and American actress and theatre practitioner. She originated the role of Martha in the 1962 Broadway premiere of Who's Afraid of Virginia Woolf? by Edward Albee, who called her "a profoundly truthful actress." Because Hagen was on the Hollywood blacklist, in part because of her association with Paul Robeson, her film opportunities dwindled and she focused her career on New York theatre.

She later became a highly influential acting teacher at New York's Herbert Berghof Studio and authored best-selling acting texts, Respect for Acting, with Haskel Frankel, and A Challenge for the Actor. Her most substantial contributions to theatre pedagogy were a series of "object exercises" that built on the work of Konstantin Stanislavski and Yevgeny Vakhtangov.

She was elected to the American Theater Hall of Fame in 1981. She twice won the Tony Award for Best Actress in a Play and received a Special Tony Award for Lifetime Achievement in 1999.

Born in Göttingen, Germany, daughter of Thyra A. (née Leisner), a trained opera singer, and Oskar Hagen, an art historian and musician, Hagen and her family emigrated to the United States in 1924. Uta was raised in Madison, Wisconsin; her father taught at the University of Wisconsin–Madison. Her early years in Germany were likely affected by the growing political changes in Europe, which would have added a layer of complexity to their decision to emigrate. She appeared in productions of the University of Wisconsin High School and in summer stock productions of the Wisconsin Players. She studied acting briefly at the Royal Academy of Dramatic Art in 1936. After spending one semester at the University of Wisconsin–Madison, where her father was the head of the department of art history, she left for New York City in 1937. Her first professional role was as Ophelia opposite Eva Le Gallienne in the title role of Hamlet in Dennis, Massachusetts, in 1936.

Hagen was cast, early on, as Ophelia by the actress-manager Eva Le Gallienne. Hagen went on to play (at age 18) the leading ingénue role of Nina in a Broadway production of Anton Chekhov's The Seagull with Alfred Lunt and Lynn Fontanne. "The Lunts," she later stated, "were an enormous influence on my life." She admired "their passion for the theatre, and their discipline." The New York Times' critic Brooks Atkinson hailed her Nina as "grace and aspiration incarnate."

She played George Bernard Shaw's Saint Joan (1951) on Broadway, and Desdemona in a production which toured. Later she acted with Paul Robeson in Shakespeare's Othello; her then-husband José Ferrer was Iago. She took over the role of Blanche DuBois in A Streetcar Named Desire for the national tour, which was directed by Harold Clurman. In Respect for Acting, she credited her discoveries with Clurman as the springboard for what she would later explore with her husband Herbert Berghof: "how to find a true technique of acting, how to make a character flow through me." She played Blanche (on the road and on Broadway) opposite at least four different Stanley Kowalskis, including Anthony Quinn and Marlon Brando.

Primarily noted for stage roles, Hagen won her first Tony Award in 1951 for her performance as the self-sacrificing wife Georgie in Clifford Odets' The Country Girl. She won again in 1963 for originating the role of Martha in Edward Albee's Who's Afraid of Virginia Woolf?. In 1981 she was elected to the American Theater Hall of Fame and in 1999 received a "Special Lifetime Achievement Tony Award."

Although she appeared in some movies after 1972, the Hollywood blacklist limited her output in film and television. She would later comment about being blacklisted, "that fact kept me pure."