Artificial Intelligence (AI) holds promise as a technology that can be used to improve government and economic policy-making. This paper proposes a new research agenda towards this end by introducing Social Environment Design, a general framework for the use of AI for automated policy-making. The position of this paper is that Social Environment Design should be further studied as a research agenda by the Reinforcement Learning, EconCS, and Computational Social Choice communities. The framework extends mechanism design to capture a fully general economic environment, including voting on policy objectives, and gives a direction for the systematic analysis of government and economic policy through AI simulation. We highlight key open problems for future research in AI-based policymaking. By solving these challenges, we hope to achieve various social welfare objectives, thereby promoting more ethical and responsible decision making.