Sustainable finance connects monetary systems with social and environmental priorities, using financial tools to balance the economy, society, and the environment across time and space. This chapter defines sustainable finance as both a proactive approach—aligning investments with sustainability goals—and a reactive tool for managing systemic risks that threaten financial stability. It highlights how short-term profit motives, conflicting stakeholder interests, and vague measurement standards hinder the effectiveness of sustainability strategies. Unsustainable consumption and production patterns accelerate climate risks and resource depletion, deepening inequality and geopolitical tensions. In response, governments have introduced frameworks like the EU Green Deal, which promotes sustainable investment through taxonomy systems, disclosure rules, and financial instruments. The chapter outlines the handbook’s structure and the contributions of its individual sections. It also draws connections across chapters to highlight overarching insights. To support the handbook’s goal of offering clear overviews and perspectives, key content is summarized in a series of tables. These tables provide a concise and consistent view of the topics and findings presented throughout the handbook. A final summary synthesizes the collective evidence and conclusions from all chapters.