Large marine areas and regional seas present a challenge in terms of management. They are often bordered by numerous maritime jurisdictions; with multi-use and multi-sector environments; involving varying governance arrangements; and generation of sufficient levels of data to best inform decision-makers. Marine management at the regional scale involves a range of mechanisms and approaches to ensure all relevant stakeholders have an opportunity to engage in the process; and these approaches can differ in their legal and regulatory conditions. At present, no such comparable structures exist at the transnational level for the ecosystem-based management of the Celtic Sea. Against this backdrop, a participative process, involving representatives from differing sectors of activity in the Celtic Sea spanning four Member States, was established for the purpose of identifying realistic and meaningful management principles in line with the goals of the Marine Strategy Framework Directive.