B-WaterSmart will accelerate the transformation to water-smart economies and societies in coastal Europe and beyond. We will apply a large-scale systemic innovation approach to select, connect and demonstrate a tailored suite of technology, management and smart data solutions for multiple users and sectors, and create new business models based on circular economy and water-smartness. We bring together six cities and regions as living labs with high ambitions to address water-related challenges and opportunities – Alicante (ES), Bodø (NO), Flanders (BE), Lisbon (PT), East Frisia (DE), Venice (IT) – selected for complementarity of scale, users, sectors and challenges, and for opportunities of mutual learning, replication & upscaling through a network of followers already mobilised. We built each case around the actual problem-owner (water utility, municipality), a research partner, innovative solution providers and market-uptake partners (6 are SMEs), complemented by partners with specific crosscutting expertise (social sciences & humanities, IT, business development, water sector outreach). We will apply a participatory approach for co-creation & implementation of solutions through local Communities of Practice and a joint innovation alliance of problem owners, and develop recommendations for suitable governance models, regulation & policy instruments. We will deliver a novel framework to assess gains in water-smartness and sustainability at different scales. Our cases will demonstrate in real systems, at multiple scales, a range of promising technologies for water reuse/nutrient recovery, and smart data applications for more efficient, safe allocation & use of resources (water, energy, nutrients). For the apps, we build on FIWARE technology to enable interoperability and exchange across sectors, which is key for systemic change. All cases have defined criteria and target values to achieve by the project end and by 2040, and can build on synergies with other funding.