OCASO (Observatorio Costero Ambiental del Sur-Oeste, Southwest Coastal Environmental Observatory) is a transboundary initiative aimed to integrate the existing observing and modeling capabilities in order to impel the use of coastal and marine environmental information by local end-users, including administrations. The final goal is to contribute to the sustainable development of the Iberian southwest coastal regions (Alentejo and Algarve in Portugal, and Andalucía in Spain) boosting the blue economy approach. OCASO pretends to serve as a link between the local coastal and marine end-users and the national and European agencies and initiatives developing coastal and marine environmental products and services. OCASO is funded by the Cooperation Programme Interreg V A SPAIN-PORTUGAL (POCTEP) 2014-2020. The participant institutions are, from Spain, the University of Cádiz (UCA, coordinator), the Spanish Port Authority (PdE) and the Spanish Institute of Oceanography (IEO), and from Portugal the University of Algarve (UAlg) and the Navy Hydrographic Institute (IH).