Harry Mordecai (June 30, 1918 - March 27, 1995) was a versatile musician known for his contributions to traditional jazz and his proficiency with stringed instruments, particularly the banjo and guitar. Born in San Francisco, he began his musical journey during his school years, where he met fellow musician Burt Bales and explored harmonica duets and ukulele playing.

Mordecai's musical horizons expanded as he delved into the banjo and guitar, receiving instruction from local teachers. He played the guitar in the Tamalpais High School orchestra before leaving high school to join the Musicians Union. In the late 1930s, he moved to San Francisco, where he developed a deep appreciation for classic jazz through record collecting, exposing himself to the sounds of jazz legends like Louis Armstrong and Jelly Roll Morton.

His connection with Lu Watters, who possessed an extensive collection of jazz recordings, led to collaborations in 1940. Mordecai's banjo skills became a key element in the post-war Lu Watters band, contributing to their unique sound. He continued to perform in various musical capacities, both in jazz and with stringed instruments, well into the 1980s.