Wesley Lawrence Willis (May 31, 1963 – August 21, 2003) was an American musician and visual artist. Diagnosed with schizophrenia in 1989, Willis began a career as an underground singer-songwriter in the outsider music tradition. Willis' songs are typically partially spoken in an MC style, and partially sung in a nasal and out-of-tune manner reminiscent of punk rock vocals. They feature bizarre, humorous and sometimes obscene or absurd lyrics sung over backing created by using the auto accompaniment feature on his Technics KN keyboard. His songs cover a wide variety of topics, with mental illness and consumerism being the most prominent themes.

Willis gained a large cult following in the 1990s, particularly after the release of his 1995 Greatest Hits album on the Alternative Tentacles label. Jello Biafra compiled the album's track list. In addition to a large body of solo musical work, Willis fronted his own punk rock band, the Wesley Willis Fiasco, during the 1990s. He was a visual artist long before he developed an interest in music, and produced hundreds of intricate, unusual, colored ink-pen drawings, most of them depicting Chicago streetscapes; he frequently sold these on the street for between $20 and $40.

Despite his mainly underground career, Willis has influenced a variety of media. For example, music software company Nullsoft took their slogan "It really whips the llama's ass!" for Winamp from Willis's song "Whip the Llama's Ass".