A microgenre is a specialized or niche genre, often used to describe narrowly defined subcategories within music, literature, film, or art. The term has been in use since at least the 1970s, particularly in the context of music, where it refers to specific stylistic offshoots of prominent genres, such as the many sub-subgenres of heavy metal and electronic music.

Originally, microgenres were labels retroactively applied by record collectors and dealers, often to increase the perceived value of rare or obscure recordings. Early examples include Northern soul, freakbeat, garage punk, and sunshine pop.

By the late 2000s and early 2010s, the creation and dissemination of microgenres had become increasingly associated with internet culture, where online platforms facilitated their rapid emergence, which was often tied to internet aesthetics and online trends. Notable internet-based microgenres include chillwave, witch house, seapunk, shitgaze, dreampunk, and vaporwave.

Hyper-specific categories and subgenres have always been prominent in popular culture. In a 1975 French article about historical fiction, "microgenre" and "macrogenre" were invoked as concepts. The author defined microgenres as "a narrowly defined group of texts connected in time and space", whereas macrogenres are "more diffuse and harder to generalize about." Further discussion of the microgenre concept appeared in various critical works of 1980s and 1990s.

Historically, musical microgenres were usually labelled by writers seeking to define a new style by linking together a group of seemingly disparate artists. The process of recognition for "power pop" was similarly formulated by a circle of rock writers who advocated their own annotated history of the genre. Music journalist Simon Reynolds has suggested that early examples of "genre-as-retroactive-fiction" include "Northern soul" and "garage punk", both of which were coined in the early 1970s, but did not become widespread until years after the fact. These genres were later followed by "freakbeat" coined by Phil Smee in the 1980s, as well as "sunshine pop" which was coined in the 1990s.

According to Reynolds, such "semi-invented" genres were sometimes pushed by record dealers and collectors to increase the monetary value of the original records. In the early 1980s, Robert Christgau coined the term "pigfuck" to describe the music of Sonic Youth, the term later took a life of its own to denote a specific style of noise rock music.

Successful attempts that resulted in widespread usage include "post-rock" (Reynolds) and "hauntology" (Mark Fisher). In the mid 1990s, Melody Maker journalists went so far as to make up fictional bands to justify the existence of an updated New Romantic scene they dubbed "Romantic Modernism". That same decade, there was a trend of electronic and dance music producers who created specialized descriptions of their music as a way to assert their individuality. In the instance of trance music, this desire led to progressive trance, Goa trance, deep psytrance, and hard trance. House, drum-n-bass, dubstep and techno also contain a large number of microgenres.

In the early 2000s, the concept of microgenres gained prominence during the digital age, proliferating through the early blogosphere, and despite its earlier history, is more often associated with these later trends. The speed at which microgenres achieve recognition and familiarity also accelerated substantially. This 21st-century "microgenre explosion" was partly a consequence of "software advances, faster internet connections, and the globalized proliferation of music."