Cancer Grand Challenges is a global initiative founded in 2020 by the two largest funders of cancer research in the world: Cancer Research UK and the US National Cancer Institute. This partnership builds on the success of Cancer Research UK’s Grand Challenge, launched in 2015 and supporting 16 multidisciplinary teams across 16 countries. By daring global teams of multidisciplinary researchers to come together and think differently, we can find bold new solutions to challenges which have confounded scientists for many years.