William McKinley Gillum (11 September 1904 - 29 March 1966), known as Jazz Gillum, was an American blues harmonica player.

He was born in Indianola, Mississippi. After running away from home at the age of 7, Bill Gillum spent the next few years in Charleston, Mississippi, working and playing for tips on local street corners. He moved to Chicago in 1923, meeting up with guitarist Big Bill Broonzy. The duo started working club dates around the city and, by 1934, Gillum started recording for ARC and Bluebird Records.

With his characteristic high, reedy harmonica sound, he appeared on many of the highly popular "Bluebird beat" recordings produced by Lester Melrose in the 1930s and 1940s, under his own name and as a sideman. However, after the Bluebird label folded in the late 1940s he made few further recordings, dying in Chicago as a result of a gunshot wound.

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