Anecdotally, people often report feeling despair about the political status quo. We conceptualise these feelings as political despair. But what is political despair, and what are its effects? We adapt intergroup emotion theory to analyse political despair in the context of racial inequality (Studies 1 and 2) and climate change (Study 3). Three cross-sectional studies (total N = 866) tested the measurement of political despair (relative to anger and hope), its pattern of appraisals and outcomes for conventional and radical actions along with well-being (stress, burnout and optimism). Structural equation modelling differentiated political despair from anger and hope and found that despair is associated with evaluations that the situation is both illegitimate and intractable (unchangeable). Moreover, political despair consistently had a negative relationship with well-being and positive relationships with conventional and radical collective action. The results suggest political despair is negatively associated with well-being and impact people's engagement in action for social change.