Existing norms, rules, and institutions seem insufficient to govern solar geoengineering in the long term. This chapter recommends additional and feasible measures to help ensure that it is researched, developed, and – if appropriate – used in ways that improve human well-being, are sustainable, and are consistent with widely shared norms. This will be challenging for reasons such as political contestation, conflicting desires for early governance and the reduction of uncertainty, and the endeavor's speculative nature. The suggestions are divided into rough stages of indoor and small-scale outdoor research, large-scale outdoor research, and deployment. The suggested forms of governance are norms, standards, and best practices; cooperation among nonstate actors; institutionally affiliated committees; state law; international institutions, including one dedicated to solar geoengineering; and – most speculatively – a multilateral agreement. Among governance's functions are reducing uncertainty and environmental risks, synthesis and assessment of results, public engagement, and preventing premature implementation, international tensions, and harmful abatement displacement.