American folk music, also known as roots music, is a broad category of music including Bluegrass, country music, gospel, old time music, jug bands, Appalachian folk, blues, Cajun and Native American music. The music is considered American either because it is native to the United States or because it developed there, out of foreign origins, to such a degree that it struck musicologists as something distinctly new. It is considered "roots music" because it served as the basis of music later developed in the United States, including rock and roll, rhythm and blues, and jazz.

Many Roots musicians do not consider themselves to be folk musicians; the main difference between the American folk music revival and American "Roots music" is that Roots music seems to cover a slightly broader range, including blues and country.

Roots musical forms reached their most expressive and varied forms in the first two to three decades of the 20th century. The Great Depression and the Dust Bowl were extremely important in disseminating these musical styles to the rest of the country, as Delta blues masters, itinerant honky tonk singers and Latino and Cajun musicians spread to cities like Chicago, Los Angeles and New York. The growth of the recording industry in the same approximate period was also important; increased possible profits from music placed pressure on artists, songwriters and label executives to replicate previous hit songs. This meant that fads like Hawaiian slack-key guitar never died out completely as rhythms or instruments or vocal stylings were incorporated into disparate genres. By the 1950s, all the forms of roots music had led to pop-oriented forms. Folk musicians like the Kingston Trio, pop-Tejano and Cuban-American fusions like boogaloo, chachacha and mambo, blues-derived rock and roll and rockabilly, pop-gospel, doo wop and R&B (later secularized further as soul music) and the Nashville sound in country music all modernized and expanded the musical palette of the country.

The roots approach to music emphasizes the diversity of American musical traditions, the genealogy of creative lineages and communities, and the innovative contributions of musicians working in these traditions today. In recent years roots music has been the focus of popular media programs such as Garrison Keillor's public radio program A Prairie Home Companion and the feature film by the same name.

Notable roots musicians have included Jelly Roll Morton, Blind Lemon Jefferson, Robert Johnson, Bessie Smith, Burl Ives, Pete Seeger, Woody Guthrie, Son House, Leadbelly, Hazel Dickens, Jimmie Rodgers, Bill Monroe, Lester Flatt and Earl Scruggs, Roy Acuff, Hank Williams, Merle Travis, Townes Van Zandt, Johnny Cash, Maggie Simpson, Mahalia Jackson, Muddy Waters, John Lee Hooker, B.B. King, Washington Phillips, Fiddlin' John Carson (1868 - 1949), Willie Nelson, and Jean Ritchie. More recent musicians who occasionally or consistently play roots music include Keb' Mo', Ralph Stanley, John Denver, Chris Castle, Ricky Skaggs, and Jeremy Fisher.