An American blues harmonica player and singer, and the first to use the name Sonny Boy Williamson.

He was born near Jackson, Tennessee in 1914. His original recordings were considered to be in the country blues style, but he soon demonstrated skill at making harmonica a lead instrument for the blues, and popularised it for the first time in a more urban blues setting. He has been called the father of modern blues harp. While in his teens he joined Yank Rachell and Sleepy John Estes playing with them in Tennessee and Arkansas, and in 1934 settled in Chicago.

He first recorded for Bluebird Records in 1937 and his first recording, Good Morning, School Girl, became a standard. He was hugely popular among black audiences throughout the southern US as well as in the midwestern industrial cities such as Detroit and his home base in Chicago, and his name was synonymous with the blues harmonica for the next decade. HIs style influenced a large number of blues harmonica performers, including Billy Boy Arnold, Junior Wells, Sonny Terry, Little Walter and Snooky Pryor among many others. He was the most widely heard and influential blues harmonica player of his generation. His music was also influential on many of his non-harmonica playing contemporaries and successors, including Muddy Waters, who had played guitar with Williamson in the mid-1940s and who recorded Good Morning Little Schoolgirl in 1963.

He was popular enough that by the 1940s, another blues harp player, Aleck/Alex 'Rice' Miller, from Mississippi, also began using the name Sonny Boy Williamson. Williamson is said to have objected to this, although no legal action took place, possibly due to the fact that Miller did not release any records during Williamson's lifetime, and that Williamson played mainly around the Chicago area, while Miller seldom ventured beyond the Mississippi Delta region until after Williamson's death. However, his legacy has since been overshadowed by that of Miller.