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 ordinary or usual;
• something that is familiar to the masses;
• 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 sometimes used as a pejorative term. In the United States, mainline churches are sometimes referred to synonymously as "mainstream."

In film

Mainstream films can best be defined as commercial films that have a wide release and play in first run theatres (A movie theater that runs primarily mainstream film fare from the major film companies and distributors, during the initial release period of each film). Being sold at popular stores, or more typically, at general stores can also be an indicator. Hollywood movies are usually considered mainstream and blockbusters are also mainstream films. The boundary is vague. Mainstream suggests middle-of-the-road and implies commercial viability, sometimes implying that the commercial viability is tantamount to a loss of artistic creativity. The opposite of mainstream film may be experimental film, art film or cult film.

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, or soft rock; but it should be noted that older generations often dislike 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 extreme 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.