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