The CNRM-CM5.1 global climate model, developed by CNRM-GAME and Cerfacs, is designed to contribute to Phase 5 of the Coupled Model Intercomparison Project (CMIP5). This paper describes its main features and provides a preliminary assessment of its mean climatology. CNRM-CM5.1 includes the atmospheric model ARPEGE-Climat (v5.2), the ocean model NEMO (v3.2), the land surface scheme ISBA, and the sea ice model GELATO (v5), coupled through the OASIS (v3) system. Key improvements over CMIP3 include increased horizontal resolution in both the atmosphere (from 2.8° to 1.4°) and the ocean (from 2° to 1°), a revised dynamical core for the atmospheric component, a new radiation scheme, and improved treatments of tropospheric and stratospheric aerosols. The land surface scheme ISBA has been externalized through the SURFEX platform, incorporating new developments such as a parameterization of sub-grid hydrology, a new freezing scheme, and a new bulk parameterization for ocean surface fluxes. The ocean model, based on the state-of-the-art version of NEMO, has also seen significant advancements. The coupling between components through OASIS has been optimized to avoid energy loss and spurious drifts. These improvements generally lead to a more realistic representation of recent mean climate and reduced drifts in preindustrial integrations. However, some biases remain, particularly in precipitation and radiative terms, and a pronounced drift in three-dimensional salinity is observed. The paper also discusses the model setup, external forcing, and performance evaluation, highlighting the model's strengths and weaknesses.The CNRM-CM5.1 global climate model, developed by CNRM-GAME and Cerfacs, is designed to contribute to Phase 5 of the Coupled Model Intercomparison Project (CMIP5). This paper describes its main features and provides a preliminary assessment of its mean climatology. CNRM-CM5.1 includes the atmospheric model ARPEGE-Climat (v5.2), the ocean model NEMO (v3.2), the land surface scheme ISBA, and the sea ice model GELATO (v5), coupled through the OASIS (v3) system. Key improvements over CMIP3 include increased horizontal resolution in both the atmosphere (from 2.8° to 1.4°) and the ocean (from 2° to 1°), a revised dynamical core for the atmospheric component, a new radiation scheme, and improved treatments of tropospheric and stratospheric aerosols. The land surface scheme ISBA has been externalized through the SURFEX platform, incorporating new developments such as a parameterization of sub-grid hydrology, a new freezing scheme, and a new bulk parameterization for ocean surface fluxes. The ocean model, based on the state-of-the-art version of NEMO, has also seen significant advancements. The coupling between components through OASIS has been optimized to avoid energy loss and spurious drifts. These improvements generally lead to a more realistic representation of recent mean climate and reduced drifts in preindustrial integrations. However, some biases remain, particularly in precipitation and radiative terms, and a pronounced drift in three-dimensional salinity is observed. The paper also discusses the model setup, external forcing, and performance evaluation, highlighting the model's strengths and weaknesses.