Ombudsman institutions (OIs) act as the guardians of citizens’ rights and as a mediator between citizens and the public administration. While the very existence of such institutions is rooted in the notion of open government, the role they can play in promoting openness throughout the public administration has not been adequately recognized or exploited. Based on a survey of 94 OIs, this report examines the role they play in open government policies and practices. It also provides recommendations on how, given their privileged contact with both people and governments, OIs can better promote transparency, integrity, accountability, and stakeholder participation; how their role in national open government strategies and initiatives can be strengthened; and how they can be at the heart of a truly open state.