The Ocean Health Index is a valuable tool for the ongoing assessment of ocean health. Using a quantitative, comprehensive method, the index evaluates the ecological, social, economic, and political conditions for the coastal waters of the world’s 221 countries and territories with ocean shorelines. This provides a means to analyse the state of the oceans, and thus it enables comprehensive ocean policy, at the same time providing a comparative measure, thus informing decisions about how to use or protect marine ecosystems. The Index is a collaborative effort, made possible through contributions from more than 65 scientists/ocean experts and partnerships between organizations including the National Center for Ecological Analysis and Synthesis, Sea Around Us, Conservation International, National Geographic, and the New England Aquarium.