Illegal, unreported and unregulated fishing, or IUU fishing, is considered one of the most significant threats to the sustainability of fisheries resources. Since the adoption of the International Plan of Action to Prevent, Deter and Eliminate Illegal, Unreported and Unregulated Fishing (IPOA-IUU), States and regional fisheries management organisations have made sustained efforts to address the problem. This book analyses the concept of IUU fishing and the international instruments which provide the legal and policy framework to combat IUU fishing. The book also examines the range of measures adopted by States and regional organisations to address IUU fishing. These measures include flag State, coastal State, port State, and market State measures.