Performance Action looks to advance the understanding of how art activism works in practice, by unpacking the relationship between the processes and politics that lie at its heart. Focusing on the UK but situating its analysis in a global context of art activism, the book presents a range of different cases of performance-based art activism, including the anti-oil sponsorship performances of groups like Shell Out Sounds and BP or not BP?, the radical pedagogy project Shake!, the psychogeographic practice of Loiterers Resistance Movement, and the queer performances of the artist network Left Front Art. Based on participatory, ethnographic research, Performance Action brings together a wealth of first-hand accounts and interviews followed by in-depth analysis of the processes and politics of art activist practice. The book is unique in that it adopts an interdisciplinary approach that borrows concepts and theories from the fields of art history, aesthetics, anthropology, sociology and performance studies, and proposes a new framework for a better understanding of how art activism works, focusing on processes. The book argues that art activism is defined by its dual nature as aesthetic-political practice, and that this duality and the way it is manifested in different processes, from the building of a shared collective identity to the politics of participation, is key towards fully understanding what sets apart art activism from other forms of artistic and political practice. The book is aimed at both specialist and non-specialist audiences, offering an accessible and engaging way into new theoretical contributions in the field of art activism, as well as on wider subjects such as participation, collective identity, prefiguration and institutional critique.