As future doctors we call on the Wellcome Trust and the Bill and Melinda Gates Foundation to remove their investments from fossil fuel companies. We share a responsibility to our future patients to address unmitigated climate change – described as “the biggest health threat of the 21st century” – and to advocate for a transition to a healthier, more sustainable economy. The British Medical Association has already divested and many other medical and health organisations are following suit. Continued investment in the fossil fuel industry violates health workers’ obligations to do no harm and grants the industry the social licence to explore and exploit still further reserves, resulting in catastrophic global warming.