Green bonds have evolved from niche to systemically relevant instruments for reallocating capital toward a low-carbon, circular economy. This book offers a rigorous, accessible guide to green finance--using Europe as the main laboratory--and maps the landscape of labelled instruments while addressing risks such as greenwashing and data fragmentation. It traces the regulatory architecture--from the EU Taxonomy to the European Green Bond framework and supervisory standards--showing how credible definitions, disclosure, and verification underpin market integrity. The book also clarifies how green bonds differ from conventional debt through use-of-proceeds discipline, ex-ante/post-issuance reporting, and independent external review. Its empirical core examines primary-market issuance yields (the greenium): once controlling for rating, sector, size, and timing, the average greenium is not statistically different from zero; any discount is concentrated in the market's early expansion and appears tied to scarcity and disclosure credibility rather than the label per se. Finally, the book provides a forward agenda on taxonomy alignment, decision-useful MRV/assurance, and the role of AI in impact measurement and risk management. The volume serves scholars, students, regulators, and practitioners financing environmentally sustainable projects.