Nick St. Nicholas (born Sept. 28, 1943) was the stage name used by Klaus Karl Kassbaum, who played bass for Steppenwolf from 1968 to 1971.

He was born in Hamburg, Germany in 1943. He later moved to Toronto and joined the Mynah Birds, whose other members included Rick James and Bruce Palmer. In 1965, he joined The Sparrow which also included singer John Kay and Jerry Edmonton. In 1967, he formed a group T.I.M.E. in Los Angeles and later joined Steppenwolf.