This book discovers and demonstrates the strategic values of design within the context of the third sector, a domain characterized by inherent complexity and the objective of effecting positive transformations across both economic and social dimensions. Based on seven years of research, it combines theoretical insights with hands-on empirical studies, offering a compelling narrative on the evolving roles of strategic design in third sector organisations. Through an in-depth analysis of best practices and four action research projects, the book showcases how design enables third sector organisations to uncover opportunities, manage innovation processes, and facilitate meaningful collaboration among diverse stakeholders. At its core, it introduces a design framework to illustrate how a strategic design mindset, together with methods and tools, fosters stakeholder participation and co-creation in the innovation process, and how it inspires conversations and reflections on organizational and systemic changes. The framework also offers actionable strategies for design researchers and practitioners willing to apply strategic design for addressing complex societal problems through creativity, innovation strategy and a systemic lens.