The scientific and policy needs for coordinated, worldwide information-gathering on ocean acidification and its ecological impacts are now widely recognized. The importance of obtaining such measurements has been endorsed by the United Nations General Assembly1, and by many governmental and non-governmental bodies who have recently assisted the scientific community in developing the Global Ocean Acidification Observing Network (GOA-ON). The design and foundation of the Network comes from two international workshops held at the University of Washington, Seattle, USA, in June 2012 and at the University of St. Andrews, UK, in July 2013 involving over a hundred participants and over 30 nations. The policy need relates to the requirement for robust evidence on ocean acidification and its worldwide impacts, to inform appropriate management action at both national and international levels. The scientific need is for large-scale, longterm data, to improve understanding of relevant chemical and biological processes; assist in the design and interpretation of experimental studies; and thereby improve predictive skills. Three high level goals of the Network aim to provide measurements for management while also delivering scientific knowledge: to improve our understanding of global ocean acidification conditions (Goal 1); to improve our understanding of ecosystem response to ocean acidification (Goal 2); and to acquire and exchange the data and knowledge necessary to optimize the modeling of ocean acidification and its impacts (Goal 3). This GOA-ON Requirements and Governance Plan provides both broad concepts and key critical details on how to meet these goals. In particular, it defines: the Network design strategy; ecosystem and goal-specific variables; spatial and temporal coverage needs; observing platform-specific recommendations; data quality objectives and requirements; initial GOA-ON products, outcomes, and applications; GOA-ON’s proposed governance structure; and Network support requirements. International OA data sharing arrangements are proposed based on defined data and metadata standards and open access to observing data. While the ocean carbon community has a relatively mature data-sharing process, it is recognized that the addition of coastal sites, as well as biological and ecological data to this framework, will take time and effort to structure. The effort of GOA-ON to develop the optimal observing system to detect ecosystem impacts of ocean acidification on various types of ecosystem (including tropical, temperate, and polar regional seas; warm and cold-water corals; and nearshore, intertidal and estuarine habitats), and in the context of other stressors, has only started recently. Further work will be needed to refine detailed protocols for relevant biological observations on a habitat- or regionally-specific basis. The potential scope for such observations is extremely wide; it is therefore essential that GOA-ON builds on, and is conceptually part of, the Framework for Ocean Observation developed by the Global Ocean Observing System (GOOS) and the International Ocean Carbon Coordination Project (IOCCP), while also working closely with the Intergovernmental Oceanographic Commission (IOC) of the United Nations Educational, Scientific and Cultural Organization (UNESCO), the Ocean Acidification International Coordination Center (OA-ICC) of the International Atomic Energy Agency (IAEA), and other relevant bodies. The GOA-ON website, , has been developed to include the latest version of the interactive of global ocean acidification observing activities. This map represents the best information available on the current inventory of GOA-ON observing assets, and provides a tangible means for increasing awareness and coordination between network partners and others with interests as well as access to ocean acidification data being collected around the globe. Future actions of the Network include facilitating additional measurement efforts in geographic areas of high concern, together with associated capacity-building; strengthening of linkages with experimental and theoretical studies; maintaining and extending communications with the ocean observing community; establishing effective and quality-controlled international data management and data sharing, through distributed data centers; and encouraging the development of synthesis products based on GOA-ON measurements. All this will require that the Network secure the necessary level of support and resources to achieve these actions.