Mainstream is, generally, the common current of thought of the majority. It is a term most often applied in the arts (i.e., music, literature, and performance). This includes:

• something that is available to the general public;
• something that has ties to corporate or commercial entities.

As such, the mainstream includes all popular culture, typically disseminated by mass media. The opposite of the mainstream are subcultures, countercultures, cult followings, underground cultures and (in fiction) genre. Additionally, mainstream is sometimes a codeword used for an actual ethnocentric or hegemonic subculture point of view, especially when delivered in a culture war speech. It is often used as a pejorative term. In the United States, mainline churches are sometimes referred to synonymously as "mainstream."

In literature

In literature, particularly in literary criticism, "mainstream" is used to designate traditional realistic or mimetic fiction, as opposed to genre fictions such as science fiction, romance novels and mysteries, as well as to experimental fiction.

In music

Mainstream music denotes music that is familiar and unthreatening to the masses, as for example popular music, pop music, middle of the road music, rap or soft rock; but it should be noted that older generations often have a well-founded dislike for the mainstream taste of the youth, and may not agree as to what is or is not mainstream. Mainstream jazz is generally seen as an evolution of be-bop, which was originally regarded as radical.

Opposing mainstream music is the music of subcultures. This exists in virtually all genres of music and is found commonly in punk rock, indie rock, anti-folk and Heavy Metal, among others. In the 1960s this music was exemplified by the music of the hippie counterculture. In more recent years alternative rock, such as the music of Nirvana, has managed to express musical nonconformity while still working within the confines of the mainstream music market.

Punk rock has distinguished itself from other non-mainstream genres by self-asserting an active anti-mainstream social movement that resists commercialism and corporate control. The punk subculture generally frowns upon major label bands that play punk music that disavows the DIY punk ethic, and views them as synonymous with mainstream music. Punk has lent this stringent DIY ethic to the indie rock that surfaced in the early 1990s underground. Several anti-corporate and not-for-profit forms of alternative protest have surfaced in the punk underground, such as self-made publications know as zines, where there is greater freedom to discuss controversial (usually far left) political issues such as discrimination, LGBT community issues, feminism, antitheism, and veganism. And though often viewed as a youthful expression of rebellion by the mainstream media, modern punk embodies a range of age groups who generally disagree with the perceived homogeneity of countercultural principals and it is not uncommon for middle-aged people to form punk houses and resistance movements in the face of what they view as the widespread, unfair exploitation of human and animal rights. This modern faction is dominantly voiced through the anarcho-punk and crust punk subcultures, in attempt to combat what is seen by those groups as a general devaluation of, and profitization from, life.