The Earth System Science Partnership, which unites all major global change research programmes, declared in 2001 an urgent need to develop "strategies for Earth System management". Yet what such strategies might be, how they could be developed, and how effective, efficient and equitable such strategies would be, remains unspecified. It is apparent that the institutions, organizations and mechanisms by which humans currently govern their relationship with the natural environment and global biochemical systems are not only insufficient-they are also poorly understood. This article presents the science programme of the Earth System Governance Project, a new 10-year global research effort endorsed by the International Human Dimensions Programme on Global Environmental Change (IHDP). It outlines the concept of earth system governance as a challenge for the social sciences, and it elaborates on the interlinked analytical problems and research questions of earth system governance as an object of study. These analytical problems concern the overall architecture of earth system governance, agency beyond the state and of the state, the adaptiveness of governance mechanisms and processes as well as their accountability and legitimacy, and modes of allocation and access in earth system governance. The article also outlines four crosscutting research themes that are crucial for the study of each analytical problem as well as for the integrated understanding of earth system governance: the role of power, knowledge, norms and scale.