This article has been commissioned as part of the forthcoming Oxford Handbook of Music Revival edited by Caroline Bithell and Juniper Hill. This essay illustrates how revival movements are employed as a form of cultural activism. Selectively drawing on and reimagining historical traditions, musicians and scholars use the past to inspire and justify innovations in the present. Musical and sociocultural changes are legitimized through the invocation of authenticity, which is based on idealized criteria that are redefined for each new revival cause. Three case studies are presented from Finnish folk music. In the first, Romantic nationalists use narrative folk songs, compiled in the national epic the Kalevala, to serve nation-building agendas. In the second, amateur instrumental pelimanni music is used to rejuvenate culturally and economically depressed rural areas and to build social cohesion. In the third, professional musicians from the Sibelius Academy draw on creative processes of ancient music (e.g., oral composition and improvisation) to foster greater personal expression, artistic freedom, and avant-garde experimentalism. The postrevival impacts and legacies of these movements are discussed.