This book outlines risk management theory systematically and comprehensively while distinguishing it from academic fields such as insurance theory. In addition, the book builds a risk financing theory that is independent of insurance theory. Until now, risk management (RM) theory has been discussed while the framework of the theory has remained unclear. However, this book, unlike previous books of this type, provides risk management theory after presenting a framework for it. Enterprise risk management (ERM) is seen differently depending on ones position. For accountants, it is a means for internal control to prevent accounting fraud, whereas for financial institutions, it quantifies the risk that administrators can take to meet supervisory standards. Therefore, most of the ERM outlines are written to suit the intended uses or topics, with no systematic RM overviews. This book discusses a systematic RM theory linked to the framework of it, unlike previous books that were written according to topic. After the Enron scandal in December 2001 and WorldCom accounting fraud in June 2002, several laws were enacted or revised throughout the world, such as the SOX Act(Sarbanes-Oxley Act) in the United States and the Financial Instruments and Exchange Law and Companies Act in Japan. In this process, the COSO(Committee of Sponsoring Organizations of Treadway Commission) published their ERM framework, while the ISO (International Organization for Standardization) published their RM framework. The author believes that the competition between these frameworks was an opportunity to systematize RM theory and greatly develop it as an independent discipline from insurance. On the other hand, the Great East Japan Earthquake that occurred on March 11, 2011, caused enormous losses. Also, because pandemics and cyber risks are increasing, businesses must have a comprehensive and systematic ERM for these risks associated with their business activities.