This timely book traces the evolution of the Green Climate Fund (GCF) since its establishment in 2010. Ruth Adler investigates whether it has the legitimacy necessary to substantially contribute to the achievement of the objectives of the Paris Agreement, including limiting the increase in global average temperature to less than 2(deg)C above pre-industrial levels.Adler conducts a comprehensive study of the performance of the GCF, and addresses gaps in the existing scholarship to analyse the Fund's effectiveness. Taking a deep dive into its portfolio, she determines whether the funded projects and programs have been effective, and if they have achieved outcomes consistent with the principles of justice and equity. Chapters draw on performance reporting and independent evaluations, as well as annual reports and financial information, which indicate implementation challenges and delays. Adler ultimately argues that the Fund's legitimacy could be enhanced through reforms to its governance and contributions from a broader range of donors.This book is a crucial read for scholars and students of climate change, environmental law and public international law. It is also beneficial for practitioners and policymakers in climate policy and finance, as well as NGOs, climate activists and investors in the field.