The 15-time Grammy Award winner died in Las Vegas, his attorney said. He had struggled in recent years with diabetes.
Early on, King transcended his musical shortcomings — an inability to play guitar leads while he sang and a failure to master the use of a bottleneck or slide favored by many of his guitar-playing peers — and created a unique style that made him one of the most respected and influential blues musicians ever.
"B.B. King taps into something universal," Eric Clapton told The Times in 2005. "He can't be confined to any one genre. That's why I've called him a 'global musician.'"
King spent decades honing the craft that helped him escape the poverty of the Deep South, where he grew up on a Mississippi plantation as the son of a sharecropper who became a teenage sharecropper himself before singing and playing his way out of the cotton fields.
He was an indefatigable performer who seldom left the concert trail for more than a few days at a time. In 1956 he played 342 shows and even in his later years kept a schedule that would test the endurance of musicians half his age.
He tapped his music and oversized personality in transcending the limitations of a genre that rein in most blues musicians, forging an international identity as a beloved cultural ambassador. King collaborated with hundreds of musicians in most fields of pop music, culminating with his 1989 teaming with U2 on the Irish rock quartet's single "When Love Comes to Town," which brought him to the attention of millions of young rock fans when he was in his mid-60s.
Decades earlier, when black audiences largely moved away from listening to the blues in favor of R&B and soul performers such as James Brown and Ray Charles, King's flagging career was resuscitated when the Rolling Stones, the Animals, Clapton, Van Morrison and other white rockers of the British Invasion started singing the praises of King and other American blues musicians to their young fans.
That put King in front of an entirely new audience, and after he put out his version of the Lowell Fulson song "The Thrill Is Gone" in 1969, King went to the upper reaches of the national sales charts and in 1971 collected the first of a string of Grammy awards.