This book provides a comparative overview of the rules in EU, US and Japan law on competition. After an overview of the history and the underlying economic issues, it discusses cartels and other agreements restraining competition (ancillary agreements, R&D/specialization agreements, distribution agreements), single-firm conduct (abuse of market power/monopolization), general procedural law and merger control, as well as state measures (regulation, subsidies, etc.) are treated from a comparative perspective. In each case, the presentation of the legal system is supplemented by examples from the case law. With focus on the protection of competition in digital markets new regulatory approaches (e.g., the EU Digital Markets Act and the comparable US regulatory initiatives) are compared and current legal developments in other jurisdictions are also addressed.