American stage (stage design) designer who, in more than 360 Broadway productions from 1924, introduced several devices that became standard in 20th-century theatrical staging. One of his innovations was the transparent skeletal framework setting of Death of a Salesman (1949), which allowed separate times and places to be shown simultaneously. Mielziner's success with works as diverse as Hamlet and the musical comedy Annie Get Your Gun was due both to his unusual technical ingenuity and to his grasp of the organic function of the total stage environment.

Mielziner studied at the National Academy of Design and the Art Students League of New York and at the Pennsylvania Academy of the Fine Arts in Philadelphia. He also attended school in Paris and Vienna, then returned to the United States to study under the stage craftsmen Robert Edmond Jones and Lee Simonson, then with the Theatre Guild. He was a collaborating designer of the Lincoln Center Repertory Theatre in New York City and the Los Angeles Music Center. He designed the setting in which Michelangelo's “Pietà” was exhibited in the Vatican Pavilion at the New York World's Fair (1964–65). After 1968 he served as chairman of the American Theater Planning Board and acted as a consultant on theatrical design.