The Olympic Games claim to be exemplars of sustainability, aiming to inspire sustainable futures around the world. Yet no systematic evaluation of their sustainability exists. We develop and apply a model with nine indicators to evaluate the sustainability of the 16 editions of the Summer and Winter Olympic Games between 1992 and 2020, representing a total cost of more than US$70 billion. Our model shows that the overall sustainability of the Olympic Games is medium and that it has declined over time. Salt Lake City 2002 was the most sustainable Olympic Games in this period, whereas Sochi 2014 and Rio de Janeiro 2016 were the least sustainable. No Olympics, however, score in the top category of our model. Three actions should make Olympic hosting more sustainable: first, greatly reducing the size of the event; second, rotating the Olympics among the same cities; third, enforcing independent sustainability standards.