The 20th century has witnessed many wars, natural disasters, political and financial crises, the spread of information and communication technologies, and the expansion of global trade. These political, economical, and social events had some effect on legal systems, both in national and international levels. As these events altered the equilibrium of many contracts, legal institutions that regard the restoration of the equilibrium of reciprocal contractual undertakings were developed in the last century, such as lesion, unconscionability, unfairness, gabin, eccessiva onerosita sopravvenuta, imprevision, Wegfall der Geschafts-grundlage, i?lem temelinin cokmesi, and hardship. This book examines these institutions in the context of national, international, and transnational laws from a comparative point of view. It illustrates how the legal remedies are applied in periods of political and financial crises in the context of various legal systems. The book is the most complete study of the UNIDROIT Principles' provisions on gross disparity and hardship that also include the relevant arbitral case law.