The European Ocean Observing System (EOOS) is a coordinating framework designed to align and integrate Europe’s ocean observing capacity, promote a systematic and collaborative approach to collecting information on the state and variability of our seas, and underpin sustainable management of the marine environment and its resources. EOOS aims to provide a framework within which European marine observations can be sustained and made available on a continuous basis for applications ranging from real-time services, through ocean health to climate services. EOOS will not take ownership or control of ocean observing in Europe. Rather, EOOS will provide a light and flexible coordinating framework to help manage and improve the existing observing effort, making it more efficient and effective at different geographical scales and for different users.