The “Strategy for the Evolution of Argo in Europe” presents a strategic plan for a European initiative for the future development of this international programme aiming for: - strengthening Europe’s role in and contribution to the global Argo Programme, - supporting the implementation of the EU Marine Policy through the development and subsequent incorporation of biogeochemical sensors into the programme, - extending spatially the observations into the European and Polar Seas, as well as into the abyssal parts of the oceans, - further developing the existing data management system, and - maximising the relevant knowledge of the Seas and Oceans, e.g. their role in a changing climate. Argo is now the major and only systematic source of such data over the oceans interior. However, there is an essential need for more data, especially from polar regions and the abyssal ocean. Together with satellite observations, Argo provides critical observations of the ocean that are required to constrain the Copernicus Marine and Climate Services modelling and forecasting systems. A consistent policy for the European seas is a long-term objective of the European Union’s legislation, i.e. it’s Marine Policy. Jointly with the EU Marine Policy with its environmental pillars, the Water Framework Directive and the Marine Strategy Framework Directive several regional conventions demand a good state of the ecosystem. In addition, the Copernicus Marine Environment Monitoring Service (CMEMS) relies on quality controlled observations to provide regular and systematic reference information on the physical state, variability and dynamics of the ocean and marine ecosystems for the global ocean and the European regional seas. Improved knowledge of the physical and biogeochemical processes of the European Seas is absolutely necessary for their management, protection, and for understanding their role in the climate system. Specific aspects are the oceanic circulation, the thermohaline stratification of the seas and control factors that govern the biogeochemical cycles. This demands a sufficient amount of monitoring data over the whole water column in the European marginal seas that in a sufficient spatial and temporal resolution only can be provided by Argo. The report thus defines targets for marginal seas like the Black Sea, the Mediterranean Sea, the Nordic Seas and the polar oceans. It describes the progress necessary in monitoring biogeochemical variables. Polar regions, especially the continental ice sheets, show a higher vulnerability to global warming than other regions. The melting of the ice sheets affects the ocean and atmosphere systems, sea level changes, the global transport processes and heat and energy budgets. European interest in these areas has already led to the deployment of Argo floats in the Nordic Seas and the Southern Ocean which has dramatically increased the data availability in such regions. The report gives detailed information about the envisioned Argo monitoring system for these areas. The deepest parts of the oceans play an important role in the evolution of the surface temperature on Earth through its capability to store and transport gases and heat. The technological developments in the recent years have made it possible to test Argo floats which probe the abyssal ocean. The report gives detailed information about the state of the technology and the next steps required to start an abyssal monitoring system. Remote sensing from satellites provides an adequate tool for monitoring the sea surface height (SSH), sea surface temperature (SST) and salinity of the seas and oceans. Provision of background in-situ data is essential to the satellite community for that they can improve/validate their products. The report therefore specifies targets for temperature and salinity measurements of Argo floats near the surface. All these suggested improvements in the existing Argo network also impacts the data management system. New float technologies require data transmission modifications, too. The extension of the Argo mission requires adaptation measures in the data business. The data processing chain has to be adapted to new biogeochemical parameters. Measurements in high latitudes may suffer from missing precise locations and have to be post processed.