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 7 multidisciplinary teams across 9 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.