The ocean is essential for humanity1,2,3. Yet, inequity in ocean-based activities is widespread and accelerating4,5,6,7,8. Addressing this requires governance approaches that can systematically measure equity and track progress9. Here we present the Ocean Equity Index (OEI)—a framework for assessing and improving equity in ocean initiatives, projects and policies. We apply the index, which scores twelve criteria, to case studies at local, national and global scales. We show that the OEI can generate structured data to support evidence-based decision-making across ocean sectors and scales. As a theoretically robust and widely applicable tool, the OEI can guide the design of more equitable ocean initiatives, projects or policies, ensuring better outcomes for coastal people and marine ecosystems.
