Post-punk is a subgenre and era of rock music that emerged in late 1977 in the wake of punk rock. The concept was originally outlined by Jon Savage in his "New Musick" editorial for Sounds magazine in November 1977. The term has been noted for lacking a universally agreed-upon definition. Post-punk musicians departed from punk's fundamental elements and raw simplicity, adopting instead a broader, more experimental approach that incorporated a variety of avant-garde sensibilities and non-rock influences. Inspired by punk's energy and DIY ethic but determined to move beyond rock clichés, artists drew influence from German krautrock and experimented with styles such as funk, electronic music, jazz, and dance music; the production techniques of dub and disco; and ideas from modernist art, cinema, literature, and politics. They also established independent record labels, created visual art, staged multimedia performances, and produced fanzines. Among the early post-punk bands, only Siouxsie and the Banshees and Public Image Ltd. achieved commercial success in 1978, with debut singles reaching the top ten of the UK Chart.

Regional scenes developed across Europe alongside new wave music, the most notable being the Netherlands' Ultra movement, Germany's Neue Deutsche Welle, Spain's La Movida Madrileña, and the coldwave scenes in France, Poland, and Belgium, as well as the Soviet and Yugoslav new wave. The original post-punk era emerged in parallel with the no wave and industrial music scenes, and later provided a foundation for British new pop and the Second British Invasion in the United States. Post-punk also influenced the development of numerous alternative and independent music genres, including gothic rock, neo-psychedelia, dark wave, dance-punk, jangle pop, ethereal wave, dream pop, and shoegaze. By the mid-to-late 1980s, post-punk had largely dissipated.

During the 2000s, several New York bands incorporated post-punk influences into contemporary indie rock, leading to the dance-punk and post-punk revival. By the 2010s, Canadian, Irish, Danish and American post-punk acts later inspired London's Windmill scene and "crank wave", while post-punk became briefly associated with the internet microgenre "doomer wave", sometimes associated with Russian post-punk and darkwave acts in the early 2020s. Around the same time, regional scenes developed in Russia and Latin America.

Post-punk is an era and diverse genre that emerged from the cultural milieu of punk rock in the late 1970s. In 1976, New York poetry magazine Contact published the earliest known use of the term "post-punk" in an interview with painter and poet Jack Micheline, the interviewer asked Micheline, "What are your thoughts moving in a post-punk beat period?".

On 26 November 1977, Sounds magazine published an issue entitled "New Musick", with editorials by English journalists Jane Suck and Jon Savage. Savage wrote a piece on an emerging scene and style of music known as "new musick", suggesting that punk rock was becoming stagnant and evolving into new, more experimental forms, which he noted as "post punk projections". He mentioned Pere Ubu, while describing Throbbing Gristle and Devo as promoting "spontaneous physical reaction". He described the style as exhibiting "more overt reggae/dub influence", sounding "the same/manufactured in a factory," and characterized Subway Sect, the Prefects, Siouxsie and the Banshees, the Slits, and Wire as exploring "harsh urban scrapings/controlled white noise/massively accented drumming". Music critics Simon Reynolds, David Wilkinson, and Theo Cateforis have cited Savage's editorial as the starting point for post-punk as a musical genre.

At the time, there was a feeling of renewed excitement regarding what "new musick" would entail, with Sounds publishing numerous preemptive editorials on the topic. By 1978-79, several British publications began to use the term "new musick" interchangeably with "post-punk". Some journalists opted for the term "art punk" to describe artists "too sophisticated" and out of step with punk's dogma, though it was sometimes used by critics as a pejorative. By the 1980s, new musick had fallen out of prominence and replaced by the broad umbrella "new wave" and "post-punk" interchangeably. Subsequently, "post-punk" became differentiated from "new wave" after their styles perceptibly narrowed.

Additionally, post-punk is often understood not only as a musical genre, but also as a period of alternative music. Reynolds defined the post-punk era as occurring roughly between 1978 and 1984. He asserted that the post-punk period produced significant innovations and music on its own. He described the period as "a fair match for the sixties in terms of the sheer amount of great music created, the spirit of adventure and idealism that infused it, and the way that the music seemed inextricably connected to the political and social turbulence of its era". Writer Mimi Haddon notes that post-punk lacks a universally agreed-upon definition, and has argued that Reynolds’ account of the genre fails to reflect contemporary consensus found on the Internet, citing artists such as the Chameleons and Echo & the Bunnymen as examples that fall outside his definition of a "post-punk vanguard".

Writers such as Mimi Haddon, Simon Reynolds, David Buckley, David Wilkinson and Alex Ogg have noted that several artists associated with post-punk predated the late-1970s punk explosion. Haddon argues that the prefix “post-” in post-punk need not be understood solely in a chronological sense. Drawing on multiple linguistic meanings of "post-," through citing the definition for postmodern feminism by political theorists Carolyn Dipalma and Kathy Ferguson. Haddon proposes definitions in relation to postmodernism, noting the prefix can function as a noun ("the postmodern punk") denoting a vantage point from which one assesses punk, as well as a verb ("to post-punk"), in the sense of announcing or signposting punk's limitations and consciously or unconsciously critiques perceived shortcomings in punk while seeking new musical directions.