Alternative rock (also known as alternative music, alt-rock or simply alternative) is a category of rock music that evolved from the independent music underground of the 1970s. Alternative rock acts achieved mainstream success in the 1990s with the likes of the grunge subgenre in the United States, and the Britpop and shoegaze subgenres in the United Kingdom and Ireland. During this period, many record labels were looking for "alternatives", as many corporate rock, hard rock, and glam metal acts from the 1980s were beginning to grow stale throughout the music industry. The emergence of Generation X as a cultural force in the 1990s also contributed greatly to the rise of alternative music.

"Alternative" refers to the genre's distinction from mainstream or commercial rock or pop. The term's original meaning was broader, referring to musicians influenced by the musical style or independent, DIY ethos of late-1970s punk rock. Traditionally, alternative rock varied in terms of its sound, social context, and regional roots. Throughout the 1980s, magazines and zines, college radio airplay, and word of mouth had increased the prominence and highlighted the diversity of alternative rock's distinct styles (and music scenes), such as noise pop, indie rock, grunge, and shoegaze. In September 1988, Billboard introduced "alternative" into their charting system to reflect the rise of the format across radio stations in the United States by stations like KROQ-FM in Los Angeles and WDRE-FM in New York, which were playing music from more underground, independent, and non-commercial rock artists.

Initially, several alternative styles achieved minor mainstream notice and a few bands, such as R.E.M. and Jane's Addiction, were signed to major labels. Most alternative bands at the time, like the Smiths, one of the key British alternative rock bands during the 1980s, remained signed to independent labels and received relatively little attention from mainstream radio, television, or newspapers. With the breakthrough of Nirvana and the popularity of the grunge and Britpop movements in the 1990s, alternative rock entered the musical mainstream, and many alternative bands became successful.

Emo found mainstream success in the 2000s with multi-platinum acts such as Fall Out Boy, My Chemical Romance, Paramore and Panic! at the Disco. Bands such as the White Stripes and the Strokes found commercial success in the early 2000s, influencing an influx of new alternative rock bands that drew inspiration from garage rock, post-punk and new wave, establishing a revival of the genres.

Record companies usually sign contracts with those entertainers who are thought to become the most popular and generate the most sales. In the past, these bands were able to record their songs in expensive studios, and their works were then offered for sale through record store chains that were owned by the entertainment corporations, along with eventually selling the merchandise into big box retailers. Record companies worked with radio and television companies to get the most exposure for their artists. The people making the decisions were business people dealing with music as a product, and those bands who were not making the expected sales figures were then excluded from this system.

Before the term alternative rock came into common usage around 1990, the sorts of music to which it refers were known by a variety of terms. In 1979, Terry Tolkin used the term alternative to describe the groups he was writing about. In 1979 Dallas radio station KZEW had a late night new wave show entitled "Rock and Roll Alternative". "College rock" was used in the United States to describe the music during the 1980s due to its links to the college radio circuit and the tastes of college students. In the United Kingdom, dozens of small do it yourself record labels emerged as a result of the punk subculture. According to the founder of one of these labels, Cherry Red, NME and Sounds magazines published charts based on small record stores called "Alternative Charts". The first national chart based on distribution called the Indie Chart was published in January 1980; it immediately succeeded in its aim to help these labels. At the time, the term indie was used literally to describe independently distributed records. By 1985, indie had come to mean a particular genre, or group of subgenres, rather than simply distribution status.

The use of the term alternative to describe rock music originated around the mid-1980s; at the time, a music industry term for cutting-edge music was new music. A similar term, alternative pop, emerged around 1985.

In 1987, Spin magazine categorized college rock band Camper Van Beethoven as "alternative/indie", saying that their 1985 song "Where the Hell Is Bill" (from Telephone Free Landslide Victory) "called out the alternative/independent scene and dryly tore it apart." David Lowery, then frontman of Camper Van Beethoven, later recalled: "I remember first seeing that word applied to us... The nearest I could figure is that we seemed like a punk band, but we were playing pop music, so they made up this word alternative for those of us who do that." DJs and promoters during the 1980s claim the term originates from American FM radio of the 1970s, which served as a progressive alternative to top 40 radio formats by featuring longer songs and giving DJs more freedom in song selection. According to one former DJ and promoter, "Somehow this term 'alternative' got rediscovered and heisted by college radio people during the 80s who applied it to new post-punk, indie, or underground-whatever music."