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 and was inducted into the Blues Foundation Hall of Fame and the Rock and Roll Hall of Fame.
He was recently taken to hospital with a diabetes-related illness.
Rolling Stone magazine once ranked BB King in third place in its list of the 100 greatest guitarists of all time, just below Jimi Hendrix and Duane Allman.
A former farmhand, King was awarded his 15th Grammy award in 2009 for his album One Kind Favor.
Even until recently, King performed in at least 100 concerts a year.

However, the organisation says it will review its policy to seek alternatives.
Uefa ordered CSKA to play three Champions League home games without any fans present as punishment for a series of offences including racist chanting.
City plan to complain to Uefa over its stance after 650 vocal fans backed the home side in the 2-2 draw.
The Premier League champions do not believe the presence of supporters influenced the result but they feel the "behind closed doors" ruling was not adhered to.
City captain Vincent Kompany earlier complained his side had been punished unfairly with their supporters also banned from the Khimki Arena.
Media playback is not supported on this device
"Why the hell do we not have any fans here? What have our fans done wrong? There's no fairness in it," he said.
A Uefa statement read: "Following the match between CSKA Moscow and Manchester City, Uefa has reviewed the officials' reports and found no breach of the conditions related to a match played behind closed doors that make part of the disciplinary decision.
"Only people who were allowed to enter the stadium (clubs delegations, media, security staff, Uefa and guests of sponsorship partners) attended the match with no record of inappropriate behaviour.
"However, Uefa is reviewing the 'behind-closed-doors' policy to see if alternative solutions could be implemented in the future."
City were pegged back on Tuesday despite taking a 2-0 lead in the first half, and are without a win from their opening three games in Group E.
"You say no fans, all of a sudden you turn up and the team who has no fans is Man City. So who's getting punished? Who's being done for racism, Man City or Moscow?" added 28-year-old Belgian Kompany.
City brought the issue about supporters to the attention of Uefa.
Meanwhile, Uefa may order clubs to allow only women and children into European matches as punishment for racist behaviour by fans.
The authority's president, Michel Platini, will put forward the issue for discussion by European football's chiefs after a successful use of the scheme in Turkey in 2011, where Fenerbahce imposed the rule after a series of hooliganism incidents.
Media playback is not supported on this device
Uefa chief of press Pedro Pinto said: "The president has suggested an idea where instead of having empty stadiums only women and children are allowed into the match.
"This is just an idea at this stage but Mr Platini is open to discussing it inside Uefa to see if it is better overall for fans and for the image of football."
City are third after three games with their remaining matches at home to CSKA Moscow and Bayern Munich before a trip to Roma, who were thrashed 7-1 at home by Bayern.

The West Yorkshire Fire and Rescue Service said it had attended an incident involving two vehicles in Keighley, at 04:40 GMT.
A car parked on Greystones Drive was alight and the fire then spread to a nearby van.
The car was destroyed and the van and its contents severely damaged.
The 'King of the Blues' guitarist and singer, BB King, has died aged 89, his lawyer says.
[NEXT_CONCEPT]
Europe's governing body Uefa says no rules were broken despite fans being present at CSKA Moscow's "behind closed doors" match with Manchester City.
[NEXT_CONCEPT]
A car set on fire during a suspected arson attack also damaged a van containing furniture packed in preparation for a house move.