Here is a list of some of the most well-renowned blues artists:

Robert Johnson
He had made up his mind to become the greatest blues musician there ever was, but he didn't have any talent. But one day he went down to the crossroads at midnight and brought his guitar. He was met there by the Devil himself. The devil tuned his guitar for him and from that day on he could play guitar and sing better than any other musician ever heard. Is the story true? You decide for youself.
Robert Johnson's official site.

John Lee Hooker
Often called "King of the boogie," his driving, rythmic approach to playing guitar has become an integral part of the blues sound. He took a lot of influence from the old Delta blues and added thunderous electric guitar.
His official site.

Muddy Waters
King of the Chicago blues. One of the best slide guitar players and singers to ever play the blues. He virtually invented the modern blues band lineup: guitar, piano, bass, and harmonica. He was always very well dressed and a very dignified man. He was responsible for some of the most definitve blues recordings ever.
His official site.

BB King
Today he is the most widely known blues artist. He is best known for his work with the electric guitar. His sound has been emulated more-so than any other blues guitarist, and for a reason too. His guitar sound is so beautiful it can make you want to cry.
His official site.