The RES4CITY Accelerathon is an innovation initiative that tackles urban sustainability challenges such as energy efficiency, mobility, and water conservation. It connects entrepreneurs, researchers, and industry leaders to drive decarbonisation and collaboration. Focusing on smart energy, circular economy, green hydrogen, and water reuse, participants receive mentorship and training, culminating in a final pitch at the European Week of Regions and Cities. With 80 participants from 11 countries, finalists included CITY 5.0, UAQUE MALOKA, HYBRIGHT, and BLUEDROPS. CITY 5.0 won with its integrated EV charging and mobility solution. The event highlighted mentorship, collaboration, and investor connections for lasting impact.