The problems and challenges associated with planetary health are vast and interconnected, and are therefore requiring of research which takes an all-of-society perspective. Following calls for input from behavioural scientists in discussions about planetary health, we here present a review and synthesis of recent research on utopian thinking and lay beliefs about societal change. For some time, utopian theorists have recognised the capacity of ideals for society to motivate social change behaviour, but this has largely been ignored by behavioural scientists. However, recent research has shown that utopian thinking elicits social change behaviour among ordinary people, and that a utopia with pro-environmental content tends to be especially motivating. Furthermore, changes which are seen as increasing levels of warmth and morality in society elicit greater levels of support and motivation to bring about those changes. These findings have implications for how social movements for planetary health can proceed and provide hope for motivating the necessary social change. We present this work in the hope that it can contribute to the furtherance of efforts for the achievement of planetary health.