Beschreibung: Groundwater is one of the most important freshwater resources for mankind and for ecosystems. Assessing groundwater resources and developing sustainable water management plans based on this resource is a major field of activity for science, water authorities and consultancies worldwide. Due to its fundamental role in the Earth’s water and energy cycles, groundwater has been declared as an Essential Climate Variable (ECV) by GCOS, the Global Climate Observing System. However, within Copernicus - the European Earth Observation Programme – there is no service available yet to deliver data on this fundamental resource, nor is there any other data source worldwide that operationally provides information on changing groundwater resources in a consistent way, observation-based, and with global coverage. Filling this gap is the goal of the G3P (Global Gravity-based Groundwater Product) project, funded since the beginning of 2020 by the European Union. G3P aims at (1) capitalizing from the unique capability of GRACE and GRACE-FO satellite gravimetry as the only remote sensing technology to monitor subsurface mass variations and thus groundwater storage change for large areas with global coverage, and (2) incorporating and advancing a wealth of products on storage compartments of the water cycle that are already part of the Copernicus portfolio and will be used for separating out the groundwater storage variations from the gravity-based total terrestrial water storage, to finally (3) developing an operational global groundwater service prototype as a cross-cutting extension of the existing Copernicus portfolio. In this contribution, we present the concept of G3P and first results.