The Canadian Earth System Model, CanESM, is a global coupled Earth System Model designed to simulate climate variability and change on timescales from seasons to centuries. CanESM is developed at the Canadian Centre for Climate Modelling and Analysis (CCCma), Environment and Climate Change Canada, with inputs from other government and university stakeholders. A significant update to the model, CanESM5, has been developed for inclusion in the upcoming Coupled Model Intercomparison Project Phase 6. Beyond CMIP6, the new version of the model will provide an updated tool for climate science applications at CCCma and within Canada and will be submitted for possible integration into the operational Canadian Seasonal to Interseasonal Prediction System (CanSIPS). CanESM5 consists of the Canadian atmospheric model (CanAM) with an embedded land surface scheme and terrestrial biogeochemistry (CLASS-CTEM) and an off-the-shelf but customized ocean model (CanNEMO), which includes sea-ice and Canadian-developed ocean biogeochemistry modules (CMOC and CanOE). The components communicate through a new custom coupler, CanCPL. This special issue hosts the documentation and model evaluation papers for CanESM5.