The chapter discusses how Marine Protected Areas (MPAs) are set up to protect marine habitats and endangered species. It explains that the international rules for MPAs are based on the Law of the Sea Convention (LOSC) and regulations from the International Maritime Organization (IMO). These rules cover special areas under the LOSC and regulations for shipping, like MARPOL and Particularly Sensitive Sea Areas (PSSAs). The chapter gives an overview of the legal framework for creating and managing MPAs within and outside national borders, as well as the main political processes involved. It also points out some gaps and weaknesses in the current system.