Philosophers are increasingly examining climate emotions – feelings experienced in response to the climate crisis. Yet anger has received surprisingly little attention. This is striking, since anger is renowned for being a strong motivator of collective action against injustice and the climate crisis is widely framed as an issue of justice. We begin by clarifying the notion of “climate emotions” and the criteria for assessing their rationality. We then argue that anger is both non-instrumentally justified–because the climate crisis involves clear injustices to which anger is a fitting response–and instrumentally rational, insofar as it can motivate beneficial individual and collective action. In doing so, we identify appropriate targets of eco-anger and argue that climate obstructionists constitute its most urgent object. Our argument is empirically informed and empirically generative, generating specific hypotheses and concrete directions for empirical work on the topic. We conclude by offering recommendations for how eco-anger can be effectively mobilized in the pursuit of climate justice.