Regional Convergence in Sustainable Development Goal Performance in Portugal: A NUTS II Composite Index Approach, 2015–2023

The United Nations 2030 Agenda has intensified the need for robust tools to monitor sustainable development performance across territories. Although numerous studies assess Sustainable Development Goals (SDGs) at the national level, evidence on regional dynamics remains comparatively limited. This study develops a composite SDG performance index for the seven Portuguese NUTS II regions over the period 2015–2023 using official statistical data. The index is constructed through a transparent methodology based on indicator normalisation, explicit treatment of normative direction, equal weighting and aggregation at both goal and overall‐index levels. Beyond measuring performance levels, the study examines territorial inequality and regional convergence through sigma‐ and beta‐convergence analyses. The results reveal a general improvement in SDG performance across all Portuguese regions, accompanied by a gradual reduction in inter‐regional disparities. Evidence of both sigma‐convergence and beta‐convergence suggests that regions with lower initial levels of SDG performance experienced comparatively stronger improvements over time, indicating a catching‐up process. Nevertheless, substantial disparities persist in specific goals, particularly those related to environmental sustainability, innovation, infrastructure and territorial development. By integrating composite‐index construction with regional convergence analysis, the study contributes to the literature on subnational SDG monitoring and provides evidence relevant for territorial cohesion policies and place‐based sustainable development strategies.