Since its inception, nuclear energy has been a site of policy debate, political protest, and divergent technical appraisals. Advocates have often framed it as a source of virtually limitless energy, and numerous nations have undertaken or are considering civilian nuclear power programs. Many of those programs have struggled under the combined challenges of safety and weapons proliferation concerns, accumulating nuclear wastes, and questions of economic viability. Less visible but particularly relevant as matters of energy democracy have been the ecological and human health impacts of a global system of uranium mining and other industrial processes comprising the nuclear fuel cycle. As climate change increasingly drives global concerns, nuclear power advocates argue that it provides a uniquely valuable, low-carbon energy source. Meanwhile, critics continue to highlight not only its direct material risks but also its potential to draw attention and resources away from more sustainable forms of energy transition. This chapter surveys the conflicted history and current status of civilian nuclear energy, with particular attention to questions of democratic governance, the roles of international and national regulatory regimes, political advocacy and protest, and the role of this contested energy source at a time of global energy transitions.