Outsider music are songs and compositions by musicians who are not part of the commercial music industry who write songs that ignore standard musical or lyrical conventions, either because they have no formal training or because they disagree with formal rules. This type of music, which is often bizarre and emotionally stark, has few outlets; performers or recordings are often promoted by word of mouth or through fan chat sites, usually among communities of music collectors and music conoisseurs. Outsider musicians usually have much "greater individual control over the final creative" product either because of a low budget or because of their "inability or unwillingness to cooperate" with modifications by a record label or producer.

While a small number of outsider musicians became notable, such as Florence Foster Jenkins, an American soprano, the majority of outsider artists are appreciated for their unique, uncompromising, and sometimes, utterly terrible music. Gina Vivinetto points out that outsider musicians include Wesley Willis, a "schizophrenic former street person from Chicago with dozens of records and a cult of loyal fans to his credit." She calls the clan of outsider musicians "an elite group," even "a group of geniuses," and she lists Syd Barrett (Pink Floyd), Brian Wilson (Beach Boys) and Skip Spence (Moby Grape). There are some links between outsider music and anti-folk: the emotional starkness, the lack of formal training and the humour.

Jeffrey Lewis names Daniel Johnston as a major influence, Syd Barrett influenced antifolk's British strain, and there are similarities between the tuneless singing styles of Wesley Willis and Paul Hawkins. However, one major difference is that while many outsider musicians are famous recluses, musicians regarded as 'antifolk' are usually grouped in a collective.

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