William O. Harbach was an American television producer, director and author.

After a brief stint managing nightclub performers, Harbach got an entry level job in 1948 as editor at the NBC New York Studio. Three years later he was offered the position of producer for a new show, The Knickerbocker Beer Show, which starred Steve Allen. That show morphed into Tonight!, which went nationwide and live from New York City in June 1953.

Harbach and Allen became an award-winning team and followed their work on The Tonight Show with The Steve Allen Show, a variety series. During this time, he developed a partnership with Nick Vanoff, with whom he continued a personal and professional relationship and friendship until Vanoff's death in 1991. Harbach and Vanoff produced the acclaimed variety show The Hollywood Palace from 1964 to 1970, as well as specials for Bing Crosby, Carol Burnett, Bob Hope, and John Wayne, among others.

Harbach died December 18, 2017, in Fairfield, Connecticut. He was 98.