The core Argo system is based on an array of profiling floats which measure every 10 days temperature and salinity throughout the deep global oceans, down to 2000 meters, and deliver data both in real time for operational users and, after careful scientific quality control, for climate change research and monitoring. Argo data policy is fully open and guarantees a free access of the data to all interested users. A new phase of the Argo programme is now being implemented at international level. This new phase has two main objectives: 1/ sustain the existing global array and 2/ extend its capabilities to greater depths and to biogeochemistry. The present target is to maintain a network of at least 4000 floats, with ¼ carrying biogeochemical parameters and ¼ going to abyssal oceans. There is more than ever a pressing need to better observe the oceans. This is recognised at the highest political levels (G7, IPCC and its Special Report on the ocean and cryosphere). Developing Argo and its extensions is, in particular, one the top priorities of the G7 Future of Oceans. The overarching objective of Euro-Argo RISE (Euro-Argo Research Infrastructure Sustainability and Enhancement) is to enhance and extend the capabilities of the Argo network to provide essential ocean observations to answer new societal and scientific challenges. Euro-Argo RISE project is needed now to allow Europe to timely develop the European contribution to this new phase of Argo and engage with new teams. Euro-Argo RISE aims to secure and improve the current network as well as to set up and organise on the long term the new components of the network, extending Argo observations towards biogeochemistry, greater depth, partially ice-covered and shallower water regions within a long-term sustainability plan supported by Member States and funding agencies.