This Open Access book offers a philosophical exploration of eco-anxiety. As knowledge about the rapidly degrading living conditions on Earth becomes more accurate, the impacts of environmental problems become more visible, and Anthropocene scenarios proliferate in films, television series, and novels, eco-anxiety emerges as a global and socially widespread phenomenon. Given the scale and severity of planetary boundary transgressions, feeling anxious about the future of human and non-human life has become a fitting emotional response. But what exactly is eco-anxiety? And how can we address its adverse effects on mental health and harness its constructive behavioural responses? This book answers these questions by developing an in-depth conceptual analysis of the notion of eco-anxiety and explaining how ecological citizenship, with its focus on hope, carbon sobriety, and courage, can help us live with eco-anxiety.