Joni Mitchell's ‘Woodstock’ is one of the most recognisable songs about the 1969 festival, yet Mitchell did not attend Woodstock and instead wrote her song in a New York City hotel room. The song ‘Woodstock’, then, represents the event not as it literally happened, but as it could have been, as an idealised depiction of nostalgia for the festival and the era's utopian potential. I analyse Mitchell's song as a utopian text and investigate the political efficacy of ‘Woodstock's musical and lyrical content for Mitchell, for other artists who cover the song, and for audiences who may recognise it as the festival's ‘theme’. As her career continues, Mitchell abandons the folk-based style of her early albums, but keeps ‘Woodstock’ an active part of her performance repertoire. I trace three later versions to show that the utopianism of the original disappears as Mitchell re-imagines the song, the event and its ideological legacy.