Hydropower and storage capacity need to increase to meet the need for renewable and dispatchable power generation. According to IEA, worldwide hydro-power capacity should increase from 1,360 GW in 2021 to 1,563–1,782 GW by 2030 and up to over 2,500 GW in 2050. At the same time, hydropower refurbishment projects must implement modern sustainability standards that preserve biodiversity and contribute to climate change mitigation and adaptation. The main objective of ReHydro is to demonstrate how European hydropower can be refurbished and modernized to be fit for a leading role in the future power system respecting sustainability requirements and societal needs in a climate change context. A suite of monitoring and digital tools (performance, cavitation, machine health) implemented at demonstration sites will improve hydropower efficiency. Innovative concepts like retrofitting with pumped hydro and hybridization will make hydropower fit for future markets. ReHydro will demonstrate how biodiversity can be improved with new fish-friendly turbines, re-establishment of environmental flows, and monitored using new tools such as eDNA. Smarter use of water resources will also be implemented so that more services can be delivered to the power markets, while multi-purpose use of the water resources for navigation and recreation can be expanded and the ability to mitigate flooding and droughts is strengthened. The results from ReHydro will achieve all the expected outcomes specified in the call. The solutions will give European hydropower industries commercial advantages to utilise the global need for hydropower expansion. It is expected that ReHydro's exploitable results will create 700–1150 new jobs in the manufacturing industry, increasing the global market by 275 mill euros. ReHydro will introduce a new paradigm to boost European leadership and competitiveness in the hydropower industry and provide new sustainable solutions that are replicable at European and global levels.