Robert Lewis (March 16, 1909 – November 23, 1997) was an American actor, director, drama teacher, author and founder of the influential Actors Studio in New York in 1947.

In addition to his accomplishments on Broadway and in Hollywood, Lewis' greatest and longest lasting contribution to American theater may be the role he played as one of the foremost acting and directing teachers of his day. He was an early proponent of the Stanislavski System of acting technique and a founding member of New York's revolutionary Group Theatre in the 1930s. In the 1970s, he was the Head of the Yale School of Drama Acting and Directing Departments.

Robert Lewis was one of the original members of the Group Theatre in the 1930s and co-founder of the Actors Studio in 1947. He was active as a character actor in Hollywood for only a brief period, under contract first to Fox Studios and then MGM. Though he went on to appear in and direct Hollywood musicals, Lewis preferred the stage, eventually becoming one of the most respected directors of Broadway plays. His greatest legacy, however, may be the role he played as one of the foremost proponents and teachers of the Stanislavski Sytem of acting, or the "Method", as it came to be known in America. In the first year of teaching at The Actors Studio, his group, which met three times a week, consisted of Marlon Brando, Montgomery Clift, Maureen Stapleton, Eli Wallach, Mildred Dunnock, Jerome Robbins, Herbert Berghof, Tom Ewell, John Forsyth (I), Anne Jackson, Sidney Lumet, Kevin McCarthy (I), Karl Malden, E.G. Marshall, 'Patricia O'Neal (I)', Beatrice Straight and David Wayne (I), to name a few. In the 1970s, Lewis was the Head of the Acting and Directing Departments at The Yale School of Drama. He was inducted into the Theatre Hall of Fame in 1991.