This publication, edited by Dr. Rebecca Serna-García, compiles the abstracts of the 4th IWA-YWP Spain National Conference 2024, held from 29 to 31 October in Bilbao, Spain, which brought together more than 260 participants. The conference sought to highlight cutting-edge advancements in water research while supporting the development of the next generation of water-sector leaders. Over the course of three dynamic days, attendees benefited from a rich and diverse program featuring 10 keynote lectures by leading experts, 42 oral presentations, 15 micro-presentations, 45 posters, 4 interactive workshops, and 7 insightful roundtable sessions. This wide-ranging agenda provided an exceptional platform for exchanging ideas, fostering professional connections, and promoting collaborative learning across the water community.