Underwater gliders are intelligent and affordable platforms, useful for long-term, multi parameter marine observations. Because of their remotely controlled navigational capabilities and the high spatial and temporal resolution of their measurements in real-time, gliders have been identified to fill gaps existing in the existing ocean observing systems. Along with there rapidly growing importance in purely science driven applications, the implementation of gliders into the Global Ocean Observing System has been recognized as a key point to improve the observational capabilities of the observing systems.The objective of the GROOM proposal is the design of a new European research infrastructure to use underwater gliders for the benefit of European citizens, researcher, and industry. GROOM will define the scientific, technological and organizational/legal levels, of a European glider capacity for research and sustained observations of the oceans, in line with the other European and international initiatives for marine in-situ observations. The proposal for this new infrastructure strongly relies on EuroARGO and JERICO infrastructures which are emerging and also considers the relevant international coordinating bodies such as GOOS. The proposed technological infrastructures will be based on several dedicated 'gliderports' to maintain and operate a European fleet of gliders in coordination with US, Canadian, Australian and other similar infrastructures. This new infrastructure would be beneficial for both academic oceanographic research and operational oceanography systems on which a large number of marine activities and societal applications now rely.