The SUPREME (“Supporting Maritime Spatial Planning in the Eastern Mediterranean”) project involved public authorities in charge of MSP, as designated by the governments of four MS (GR, HR, IT and SL), and the UNEP/MAP Barcelona Convention. The SUPREME project focused on two key objectives: support the implementation of Maritime Spatial Planning in EU Member States; launch and carry out concrete and cross-border MSP initiative between Member States. SUPREME partners addressed these two key objectives through a variety of tools and considering the ecosystem-based approach. The SUPREME activities included the following: understand future and potential needs for cross-border areas and issues (including the description of human activities and ecosystem components); provide guidelines and recommendations for a conceptual methodology for cross-border aspects of MSP; establish a mechanism for cross-border cooperation in the preparation of maritime spatial planning (a regional SME platform); analysis of data needs and gaps also in relation to cross-border activities; analysis and testing of tools and methods for the MSP process; development and experimentation of stakeholder engagement approaches; analysis of the relationship between relevant policy instruments (eg MSFD, WFD, etc.); promote integration between ICZM and MSP, addressing the connection between land and sea; case studies that illustrate how the challenges of MSP implementation can be addressed.