King, known for his hits Lucille, Sweet Black Angel and Rock Me Baby, died in his sleep in Las Vegas.
Born in Mississippi, King began performing in the 1940s, going on to influence a generation of musicians, and working with Eric Clapton and U2.
Once ranked as the third greatest guitarist of all time, he had been suffering ill health in recent months. He was recently taken to hospital with a diabetes-related illness.
A former farmhand, King was awarded his 15th Grammy award in 2009 for his album One Kind Favor.
He was also inducted into both the Blues Foundation Hall of Fame and the Rock and Roll Hall of Fame.
Rolling Stone magazine placed him behind only Jimi Hendrix and Duane Allman in its list of the 100 greatest guitarists of all time.
Until recently, King performed in at least 100 concerts a year. 'Heartfelt vocals'
He fused together both jazz and blues on his beloved guitar, a Gibson ES-344 he lovingly dubbed "Lucille". In the early part of his career, he played to exclusively black audiences, but his heartfelt vocals and undeniable talent saw him embraced by a much broader fanbase as time went on - touring Europe and topping the charts.
Younger musicians such as Clapton and Steve Miller, who admired his work, introduced him to a new generation of fans in the late '60s with hits like The Thrill is Gone. Albums such as Live at County Cook Jail and BB King in London followed.
His career was reignited in the late 1980s when he duetted with U2 on When Love Comes To Town. At the turn of the millennium, aged 75, he once again achieved major commercial success with the Eric Clapton collaboration Riding With the King.
"King's is now the name most synonymous with the blues, much as Louis Armstrong's once was with jazz," critic Francis Davis wrote in his 1995 book The History of the Blues. "You don't have to be a blues fan to have heard of King."