Prisons don't work, but prisoners do. Prisons are often critiqued as unjust, but we hear little about the daily labour of incarcerated workers -- what they do, how they do it, who they do it for and under which conditions. Unions protect workers fighting for better pay and against discrimination and occupational health and safety concerns, but prisoners are denied this protection despite being the lowest paid workers with the least choice in what they do -- the most vulnerable among the working class. Starting from the perspective that work during imprisonment is not "rehabilitative," this book examines the reasons why people should care about prison labour and how prisoners have struggled to organize for labour power in the past. Unionizing incarcerated workers is critical for both the labour movement and struggles for prison justice, this book argues, to negotiate changes to working conditions as well as the power dynamics within prisons themselves.