The OYSTER project will lead to the development and demonstration of a marinized electrolyser designed for integration with offshore wind turbines. Stiesdal will work with the world’s largest offshore wind developer (Ørsted) and a leading wind turbine manufacturer (Siemens Gamesa Renewable Energy) to develop and test in a shoreside pilot trial a MW-scale fully marinized electrolyser. The findings will inform studies and design exercises for full-scale systems that will include innovations to reduce costs while improving efficiency. To realise the potential of offshore hydrogen production there is a need for compact electrolysis systems that can withstand harsh offshore environments and have minimal maintenance requirements while still meeting cost and performance targets that will allow production of low-cost hydrogen. The project will provide a major advance towards this aim. Preparation for further offshore testing of wind-hydrogen systems will be undertaken, and results from the studies will be disseminated in a targeted way to help advance the sector and prepare the market for deployment at scale. The OYSTER project partners share a vision of hydrogen being produced from offshore wind at a cost that is competitive with natural gas (with a realistic carbon tax), thus unlocking bulk markets for green hydrogen (heat, industry, and transport), making a meaningful impact on CO2 emissions, and facilitating the transition to a fully renewable energy system in Europe. This project is a key first step on the path to developing a commercial offshore hydrogen production industry and will lead to innovations with significant exploitation potential within Europe and beyond.