Crosby, Stills & Nash (CSN) was a folk-rock supergroup made up of the American singer-songwriters David Crosby and Stephen Stills and the English singer-songwriter Graham Nash. When joined by the Canadian singer-songwriter Neil Young, they were called Crosby, Stills, Nash & Young (CSNY). They are noted for their intricate vocal harmonies and lasting influence on American music and culture, their political activism and their tumultuous relationships.

David Van Cortlandt Crosby was an American singer, songwriter, and guitarist. He first found fame as a member of the Byrds, with whom he helped pioneer the genres of folk rock and psychedelia in the mid-1960s, and later as part of the supergroup Crosby, Stills & Nash, who helped popularize the California sound of the 1970s. In addition to his music, Crosby was known for his outspoken personality, politics, and personal troubles; he was sometimes depicted as emblematic of the counterculture of the 1960s.