Riley B. King was born on September 16, 1925, on a cotton plantation near the town of Itta Bena, Mississippi, the son of sharecroppers Albert and Nora Ella King. He considered the nearby city of Indianola, Mississippi to be his home. When Riley was 4 years old, his mother left his father for another man, so the boy was raised by his maternal grandmother, Elnora Farr, in Kilmichael, Mississippi.
While young, King sang in the gospel choir at Elkhorn Baptist Church in Kilmichael. It seems that at the age of 12 he purchased his first guitar for $15.00, although another source indicates he was given his first guitar by Bukka White, his mother's first cousin (King's grandmother and White's mother were sisters). In 1943, King left Kilmichael to work as a tractor driver and play guitar with the Famous St. John's Quartet of Inverness, Mississippi, performing at area churches and on WGRM in Greenwood, Mississippi.
In 1946, King followed Bukka White to Memphis, Tennessee. White took him in for the next ten months. However, King returned to Mississippi shortly afterward, where he decided to prepare himself better for the next visit, and returned to West Memphis, Arkansas, two years later in 1948. He performed on Sonny Boy Williamson's radio program on KWEM in West Memphis, where he began to develop an audience. King's appearances led to steady engagements at the Sixteenth Avenue Grill in West Memphis and later to a ten-minute spot on the Memphis radio station WDIA. The radio spot became so popular that it was expanded and became the Sepia Swing Club.
Initially he worked at WDIA as a singer and disc jockey, gaining the nickname "Beale Street Blues Boy", which was later shortened to "Blues Boy" and finally to B.B. It was there that he first met T-Bone Walker. King said, "Once I'd heard him for the first time, I knew I'd have to have [an electric guitar] myself. 'Had' to have one, short of stealing!"