Electric blues is blues music distinguished by the use of electric amplification for musical instruments. The guitar was the first instrument to be popularly amplified and used by early pioneers T-Bone Walker in the late 1930s and John Lee Hooker and Muddy Waters in the 1940s. Their styles developed into West Coast blues, Detroit blues, and post-World War II Chicago blues, which differed from earlier, predominantly acoustic-style blues. By the early 1950s, Little Walter was a featured soloist on blues harmonica using a small hand-held microphone fed into a guitar amplifier. Although it took a little longer, the electric bass guitar gradually replaced the stand-up bass by the early 1960s. Keyboards, especially electric organs and electric pianos, later became widely used in electric blues.

The blues, like jazz, probably began to be amplified in the late 1930s. The first star of the electric blues is generally recognized as being T-Bone Walker; born in Texas but moving to Los Angeles in the mid-1930s, he combined blues with elements of swing music and jazz in a long and prolific career. After World War II, amplified blues music became popular in American cities that had seen widespread African American migration, such as Chicago, Memphis, Detroit, St. Louis, and the West Coast. The initial impulse was to be heard above the noise of lively rent parties. Playing in small venues, electric blues bands tended to remain modest in size compared with larger jazz bands. In its early stages electric blues typically used amplified electric guitars, double bass (which was progressively replaced by bass guitar), and harmonica played through a microphone and a power amp or a guitar amplifier.

By the late 1940s several Chicago-based blues artists had begun to use amplification, including John Lee Williamson and Johnny Shines. Early recordings in the new style were made in 1947 and 1948 by musicians such as Johnny Young, Floyd Jones, and Snooky Pryor. The format was perfected by Muddy Waters, who utilized various small groups that provided a strong rhythm section and powerful harmonica. His "I Can't Be Satisfied" (1948) was followed by a series of ground-breaking recordings. Chicago blues is influenced to a large extent by the Mississippi blues style, because many performers had migrated from the Mississippi region. Howlin' Wolf, Muddy Waters, Willie Dixon and Jimmy Reed were all born in Mississippi and moved to Chicago during the Great Migration. In addition to electric guitar, harmonica, and a rhythm section of bass and drums, some performers such as J. T. Brown who played in Elmore James's bands or J. B. Lenoir's also used saxophones, largely as a supporting instrument. Little Walter, Sonny Boy Williamson (Rice Miller) and Big Walter Horton were among the best-known harmonica (called "blues harp" by blues musicians) players of the early Chicago blues scene and the sound of electric instruments and harmonica is often seen as characteristic of electric Chicago blues. Muddy Waters and Elmore James were known for their innovative use of slide electric guitar. Howlin' Wolf and Muddy Waters were for their deep, "gravelly" voices. Bassist and composer Willie Dixon played a major role on the Chicago blues scene. He composed and wrote many standard blues songs of the period, such as "Hoochie Coochie Man", "I Just Want to Make Love to You" (both penned for Muddy Waters) and, "Wang Dang Doodle", "Spoonful" and "Back Door Man" for Howlin' Wolf. Most artists of the Chicago blues style recorded for the Chicago-based Chess Records and Checker Records labels; there were also smaller blues labels in this era including Vee-Jay Records and J.O.B. Records.

In the late 1950s, the West Side style blues emerged in Chicago with major figures including Magic Sam, Jimmy Dawkins, Magic Slim and Otis Rush. West Side clubs were more accessible to white audiences, but performers were mainly black, or part of mixed combos. West Side blues incorporated elements of blues rock but with a greater emphasis on standards and traditional blues song forms. Albert King, Buddy Guy, and Luther Allison had a West Side style that was dominated by amplified electric lead guitar.

Memphis, with its flourishing acoustic blues scene based in Beale Street, also developed an electric blues sound during the early 1950s. Sam Phillips' Sun Records company recorded musicians such as Howlin' Wolf (before he moved to Chicago), Willie Nix, Ike Turner, and B.B. King. Other Memphis blues musicians involved with Sun Records included Joe Hill Louis, Willie Johnson and Pat Hare who introduced electric guitar techniques such as distorted and power chords, anticipating elements of heavy metal music. These players had an influence on early rock and rollers and rockabillies, many of whom also recorded for Sun Records. After Phillips discovered Elvis Presley in 1954, the Sun label turned to the rapidly expanding white audience and started recording mostly rock and roll. Booker T. & the M.G.'s carried the electric blues style into the 1960s.

Detroit-based John Lee Hooker pursued a unique brand of electric blues based on his deep rough voice accompanied by a single electric guitar. Though not directly influenced by boogie-woogie, his "groovy" style is sometimes called "guitar boogie". His first hit, "Boogie Chillen", reached #1 on the R&B charts in 1949. He continued to play and record until his death in 2001.

The New Orleans blues musician Guitar Slim recorded "The Things That I Used to Do" (1953), which featured an electric guitar solo with distorted overtones and became a major R&B hit in 1954. It is regarded as one of The Rock and Roll Hall of Fame's 500 Songs that Shaped Rock and Roll, and contributed to the development of soul music.

In the 1950s, blues had a huge influence on mainstream American popular music. While popular musicians like Bo Diddley and Chuck Berry, both recording for Chess, were influenced by the Chicago blues, their enthusiastic playing styles departed from the melancholy aspects of blues and played a major role in the development of rock and roll. Chicago blues also influenced Louisiana's zydeco music, with Clifton Chenier using blues accents. Zydeco musicians used electric solo guitar and cajun arrangements of blues standards.