Effective monitoring and evaluation (M&E) are essential for ensuring that Maritime Spatial Planning (MSP) contributes to the sustainable development of the blue economy while maintaining alignment with institutional frameworks. The study presented in this paper develops a stakeholder-driven M&E framework for sustainable MSP, emphasizing a participatory methodology to enhance the relevance and applicability of performance assessment. Using a structured mutual learning approach, the research engaged stakeholders in two iterative rounds: the first identified key strategic objectives for a sustainable blue economy through dialogue and a complementary questionnaire survey, while the second refined these into corresponding specific objectives. This process was applied in the context of a case study in Greece, where MSP implementation is shaped by national and EU regulatory frameworks and the socio-economic dynamics of the coastal and maritime sectors. The case study provided a practical testing ground for the proposed methodology, involving stakeholders from government, industry, and civil society to ensure a comprehensive perspective. The insights gained informed the design of a key performance indicator (KPI) framework, integrating qualitative and quantitative metrics tailored to the regional maritime governance landscape. These metrics were selected based on the SMARTIE (Specific, Measurable, Achievable, Relevant, Time-Bound, Inclusive, Equitable) criteria and were clearly aligned with the established objectives. The frequency of measurements, appropriate data collection methods, and indicative data sources were also defined to provide a complete KPIs framework. This stakeholder-driven methodology strengthens the adaptive capacity of MSP by ensuring continuous assessment and revision aligned with sustainability objectives and facilitating ex ante, intermediate, and ex post evaluations. The proposed framework is scalable and transferable, offering a systematic approach to improving policy coherence and decision-making across different geographic, administrative, and sectoral contexts, enabling sustainable governance and maritime governance.
