This study, the first of its kind, provides a global analysis of illegal and unreported fishing (IUU) for 54 countries and high seas regions. The authors estimate that the total value of current IUU losses worldwide ranges from $110 billion to $523.5 billion annually, representing between 11 and 26 million tons. The data reveal significant regional differences in the level and trend of IUU over the past 20 years, with a strong correlation between governance and the level of IUU. Developing countries are particularly vulnerable to IUU, with West Africa's estimated catches being 40% higher than reported. While some progress has been made in reducing IUU in certain areas, the problem remains pervasive, and the authors emphasize the need for improved governance and international cooperation to curb IUU fishing. The study provides a baseline for evaluating future efforts to address this issue.This study, the first of its kind, provides a global analysis of illegal and unreported fishing (IUU) for 54 countries and high seas regions. The authors estimate that the total value of current IUU losses worldwide ranges from $110 billion to $523.5 billion annually, representing between 11 and 26 million tons. The data reveal significant regional differences in the level and trend of IUU over the past 20 years, with a strong correlation between governance and the level of IUU. Developing countries are particularly vulnerable to IUU, with West Africa's estimated catches being 40% higher than reported. While some progress has been made in reducing IUU in certain areas, the problem remains pervasive, and the authors emphasize the need for improved governance and international cooperation to curb IUU fishing. The study provides a baseline for evaluating future efforts to address this issue.