Hardcore punk is an underground music genre that originated in the late 1970s, following the mainstream success of punk rock. Hardcore is generally faster, thicker, and heavier than earlier punk rock. The origin of the term "hardcore punk" is uncertain. The Vancouver-based band D.O.A. may have helped to popularize the term with the title of their 1981 album, Hardcore '81.

Hardcore has spawned the straight edge movement and its associated submovements, hardline and youth crew. Hardcore was heavily involved with the rise of the independent record labels in the 1980s, and with the DIY ethics in underground music scenes. It has influenced a number of music genres which have experienced mainstream success, such as metalcore, grunge, thrash metal, emo and post-hardcore. Hardcore sprouted underground scenes across the United States in the early 1980s вАФ particularly in Washington, D.C., California, New York/New Jersey, and BostonвАФas well as in the United Kingdom.

While most early punk rock songs were played with mid-tempo rock beats using simple guitar barre chords in major keys, hardcore broke from this format. Like punk, many of the players lacked musical training (with a few exceptions). The DIY aesthetic of shows being held in small venues on the floors of basements, halls, schools, etc., played into the sound. Much of the style evolved to add to the energy of the live show. Experimentation was the norm. Early recordings were of poor quality, though not by design but by budget constraints, and bands such as The Circle Jerks, Reagan Youth, Flipper, Naked Raygun, and Minor Threat recorded only as a means to promote the live performance and document the sounds they were making.

Most bands followed the traditional singer/guitar/bass/drum format. The songwriting had more emphasis on rhythm rather than melody. Hardcore vocalists screamed, chanted and used spoken word poetry. Drummers would play fast D beat one moment and then drop tempo into elaborate musical breakdowns the next. Guitarists were not afraid to play solos, octave leads, and grooves as well as tapping into the various feedback and harmonic noises available to them. The guitar sound was almost always distorted and amplified. With two minutes being considered a lengthy hardcore song, most of the songs were short and rushed.

In critic Steven Blush's description, "The Sex Pistols were still rock'n'roll...like the craziest version of Chuck Berry. Hardcore was a radical departure from that. It wasn't verse-chorus rock. It dispelled any notion of what songwriting is supposed to be. It's its own form."

This distillation of punk was further emphasized through dress. Hardcore punk fans adopted a dressed-down style of T-shirts, jeans, and crewcut-style haircuts. The style of the 1980s hardcore scene contrasted with the more provocative fashion styles of late 1970s punk rockers(elaborate hairdos, torn clothes, patches, safety pins, studs, spikes, etc.). Keith Morris, "the...punk scene was basically based on English fashion. But we had nothing to do with that. Black Flag and the Circle Jerks were so far from that. We looked like the kid who worked at the gas station or submarine shop."