A European research and innovation (R&I) initiative was launched in 2020 as a voluntary coordinated action in the European Research Area (ERA). During the German EU Council Presidency in 2020, research ministers agreed on a member state-led R&I initiative to build a European hydrogen economy. The action was started following the Competitiveness Council conclusions of December 2020 (13567/20) in which the Council invited the Commission and interested member states to conduct an agenda process on green hydrogen as an ERA pilot action in 2021, while ensuring consistency with other related EU initiatives. A total of 25 member states and five third countries came together to jointly identify the most important research needs and items for action on green hydrogen in close coordination with the European Commission, which are presented in this strategic research and innovation agenda. It transcends the format of a classic research and innovation agenda, proposing, beyond technological development, innovation measures, policy support and implementation actions to prepare for the realisation of a green and clean hydrogen economy.