Emo is a style of rock music typically characterized by melodic musicianship and expressive, often confessional lyrics. It originated in the mid-1980s hardcore punk movement of Washington, D.C., where it was known as "emotional hardcore" or "emocore" and pioneered by bands such as Rites of Spring and Embrace. As the style was echoed by contemporary American punk rock bands, its sound and meaning shifted and changed, blending with pop punk and indie rock and encapsulated in the early 1990s by groups such as Jawbreaker and Sunny Day Real Estate. By the mid 1990s numerous emo acts emerged from the Midwestern and Central United States, and several independent record labels began to specialize in the style.

Emo broke into mainstream culture in the early 2000s with the platinum-selling success of Jimmy Eat World and Dashboard Confessional and the emergence of the subgenre "screamo". In recent years the term "emo" has been applied by critics and journalists to a variety of artists, including multiplatinum acts and groups with disparate styles and sounds. In addition to music, "emo" is often used more generally to signify a particular relationship between fans and artists, and to describe related aspects of fashion, culture, and behavior.

Today emo is commonly tied to both music and fashion as well as the emo subculture. Usually among teens, the term "emo" is stereotyped with wearing slim-fit jeans, sometimes in bright colors, and tight t-shirts (usually short-sleeved) which often bear the names of emo bands. Studded belts and black wristbands are common accessories in emo fashion. Some males also wear thick, black horn-rimmed glasses. The emo fashion is also recognized for its hairstyles. Popular looks include long side-swept bangs, sometimes covering one or both eyes. Also popular is hair that is straightened and dyed black. Bright colors, such as blue, pink, red, or bleached blond, are also typical as highlights in emo hairstyles. Short, choppy layers of hair are also common. This fashion has at times been characterized as a fad. In the early 2000s, emo fashion was associated with a clean cut look, but as the style spread to younger teenagers, the style has become darker, with long bangs and emphasis on the color black replacing sweater vests. Emo has been associated with a stereotype that includes being particularly emotional, sensitive, shy, introverted, or angst-ridden. It has also been associated with depression, self-injury, and suicide.