William "Billy Boy" Arnold (born September 16, 1935)[1] is an American blues harmonica player, singer and songwriter.

Arnold is a self-taught harmonica player and has worked with blues legends such as Bo Diddley, Johnny Shines, Otis Rush, Earl Hooker, Howlin' Wolf, Muddy Waters and others.

[2] Born in Chicago, Illinois, as one of 16 children,[2] he began playing harmonica as a child, and in 1948 received informal lessons from his near neighbour John Lee "Sonny Boy" Williamson, shortly before the latter's death.

[1] The same day as the Bo Diddley sessions, Billy Boy recorded the self-penned "You Got to Love Me" which was not released until the box set Chess Blues 1947–1967 in 1992.

[1] By the 1970s, Arnold had begun playing festivals, touring Europe and recording again, including as part of the American Blues Legends '75 package organised by Big Bear Music.