Hard bop is a subgenre of jazz that is an extension of bebop (or "bop") music. Journalists and record companies began using the term in the mid-1950s to describe a new current within jazz that incorporated influences from rhythm and blues, gospel music, and blues, especially in saxophone and piano playing.

David H. Rosenthal contends in his book Hard Bop that the genre is, to a large degree, the natural creation of a generation of African-American musicians who grew up at a time when bop and rhythm and blues were the dominant forms of black American music. Prominent hard bop musicians included Horace Silver, Clifford Brown, Charles Mingus, Art Blakey, Cannonball Adderley, Miles Davis, John Coltrane, Hank Mobley, Thelonious Monk, Lee Morgan, Wes Montgomery, Pat Martino and others.

Hard bop is sometimes referred to as "funky hard bop". The "funky" label refers to the rollicking, rhythmic feeling associated with the style. The descriptor is also used to describe soul jazz, which is commonly associated with hard bop. According to Mark C. Gridley, soul jazz more specifically refers to music with "an earthy, bluesy melodic concept and...repetitive, dance-like rhythms. Some listeners make no distinction between 'soul-jazz' and 'funky hard bop,' and many musicians don't consider 'soul-jazz' to be continuous with 'hard bop.'" The term "soul" suggests the church, and traditional gospel music elements such as "amen chords" (the plagal cadence) and triadic harmonies that seemed to suddenly appear in jazz during the era. Leroi Jones noted a combination of "wider and harsher tones" with "accompanying piano chords [that] became more basic and simplified." He cited saxophonist Sonny Rollins' playing as one of the best examples of the style. Jazz critic Scott Yanow distinguished hard bop from the broader world of bop by saying that "[t]empos could be just as blazing but the melodies were generally simpler, the musicians (particularly the saxophonists and pianists) tended to be familiar with (and open to the influence of) rhythm & blues and the bass players (rather than always being stuck in the role of a metronome) were beginning to gain a little more freedom and solo space."

Hard bop has been seen by some critics as a response to cool jazz and West Coast jazz. As Paul Tanner, Maurice Gerow, and David Megill explain, "the hard bop school...saw the new instrumentation and compositional devices used by cool musicians as gimmicks rather than valid developments of the jazz tradition." However, Shelly Manne suggested that cool jazz and hard bop simply reflected their respective geographic environments: the relaxed cool jazz style reflected a more relaxed lifestyle in California, while driving bop typified the New York scene. Some writers, such as James Lincoln Collier, suggest that the style was an attempt to recapture jazz as a form of African American expression. Whether or not this was the intent, many musicians quickly adopted the style, regardless of race.

According to Nat Hentoff in his 1957 liner notes for the Art Blakey Columbia LP entitled Hard Bop, the phrase was originated by music critic and pianist John Mehegan, jazz reviewer of the New York Herald Tribune at that time. Hard bop first developed in the mid-1950s, and is generally seen as originating with the Jazz Messengers, a quartet led by pianist Horace Silver and drummer Art Blakey. Alternatively, Anthony Macias points to Detroit as an early center in the rise of bop and hard bop, noting Detroit musicians Barry Harris and Kenny Burrell and the fact that Miles Davis lived in the city from 1953 to 1954. Billy Mitchell, a tenor saxophone player, organized a band that played at the Blue Bird Inn during the early 1950s that "anchored the city's Jazz scene" and attracted hard bop musicians to the city.

Michael Cuscuna maintains that Silver and Blakey's efforts were in response to the New York bebop scene:

Both Art and Horace were very, very aware of what they wanted to do. They wanted to get away from the jazz scene of the early '50s, which was the Birdland scene — you hire Phil Woods or Charlie Parker or J. J. Johnson, they come and sit in with the house rhythm section, and they only play blues and standards that everybody knows. There's no rehearsal, there's no thought given to the audience. Both Horace and Art knew that the only way to get the jazz audience back and make it bigger than ever was to really make music that was memorable and planned, where you consider the audience and keep everything short. They really liked digging into blues and gospel, things with universal appeal. So they put together what was to be called the Jazz Messengers.

David Rosenthal sees the development of hard bop as a response to both a decline in bebop and the rise of rhythm and blues: