This thematic report focuses on the role of science advice in policymaking. By analysing key characteristics of actors, functions and roles, competencies and skills, and incentives it aims to support the description and analysis of national science-for-policy (S4P) ecosystems. This report provides a shared perspective on these ecosystems, helping countries map their systems, identify best practices, and address gaps. It emphasizes the need to enhance collaboration between scientists and policymakers, foster professional competencies, and align incentives to encourage policy-relevant research.