Walter Klien (November 27, 1928 - February 10, 1991) was an Austrian pianist.
Klien was born in Graz. His mother was the artist Erika Giovanna Klien (1900-1957). She emigrated to the United States in 1929, and their only further contact was by correspondence. Klien studied piano with Josef Dichler at the Music Academy in Vienna and with Arturo Benedetti Michelangeli. He also studied composition with Paul Hindemith.