Dennis Hans Olsen AM (born 28 February 1938) is an Australian singer, actor, director and pianist. He is best known as an exponent of the "patter" roles in Gilbert and Sullivan operas. At first trained as a pianist, Olsen soon switched to acting, beginning his career with Australian theatre companies in the 1960s. After success with Opera Australia, Olsen briefly joined the D'Oyly Carte Opera Company. He returned to Australia in 1971 playing in theatre as well as Gilbert and Sullivan over the next four decades. He also sang Noël Coward songs in his cabaret act and acted in films, television and radio.