King, 89, was one of the music world's most prolific acts. He performed a reported 15,000 times during his career, according to ABC News.
PHOTOS: B.B. King's career over the years
"What a brilliant man you were. One who will forever be noted as such an inspiration to millions globally," Gladys Knight wrote on Twitter.
Eric Clapton posted this video message on Facebook talking about his long friendship with B.B. King.
Ringo and Barbara Star wrote: "God bless BB King peace and love to his family."
God bless BB King peace and love to his family Ringo and Barbarax😎✌️🌟💖— Ringo Starr (@ringostarrmusic) May 15, 2015
County music starts Lee Brice and Travis Tritt both weighed in, as did KISS bass guitarist Gene Simmons.
B.B. King. My heart just broke into a million pieces. Not enough space to describe my feelings of the man. Legend, pure, real, teacher..— Lee Brice (@leebrice) May 15, 2015
I'm extremely saddened to learn that blues legend BB King has died! He was a great musician and an inspiring human being! May he now RIP.— Travis Tritt (@Travistritt) May 15, 2015
Dozens of actors, comedians, athletes and TV personalities also shared their thoughts of the guitar legend on social media.
RIP to a Blues Legend... B.B. King— Sugar Ray Leonard (@SugarRayLeonard) May 15, 2015
B.B. King may be gone but his music lives forever. Rest easy.— Fred Willard (@Fred_Willard) May 15, 2015
RIP BB KING. We lost one of music's brightest stars, one sure to keep shining bright for generations to come. #BBKing— Montel Williams (@Montel_Williams) May 15, 2015