The UN High Seas Treaty (formally the Agreement on the Conservation and Sustainable Use of Marine Biological Diversity of Areas Beyond National Jurisdiction under the UN Convention on the Law of the Sea) is ushering in a new era of ocean conservation at a critical point in time for ocean health. The high seas cover half the planet, or two thirds of the global ocean, and until now they have been heavily exploited and impacted, with next to no protection. Two decades of campaigning by advocates, informed by the work of many marine scientists, preceded several years of complex and contested negotiations, culminating in adoption of the world’s newest multilateral environmental agreement in 2023. 145 countries have now signed the treaty and around 90 countries have ratified, triggering its entry into force in early 2026 and the first Conference of the Parties in early 2027. For the first time, the treaty provides a comprehensive framework for regulating and protecting international waters, representing an historic milestone for global ocean governance and multilateral cooperation. The regime comprises a ‘package deal’ of four parts: marine genetic resources, area-based management tools (including marine protected areas, or MPAs), environmental impact assessments (EIAs), and capacity-building and technology transfer. This talk will briefly cover all parts of the treaty and important provisions on ‘enhanced cooperation’, focusing on the potential contribution of high seas MPAs and EIAs to ocean health and the goals of the Kunming-Montreal Global Biodiversity Framework. It will cover the importance of Traditional Knowledge, connectivity, high-level (IUCN I and II) protection, and climate-smart design in developing effective networks of marine protected areas at regional and global scales. The critical role of marine science will be addressed throughout, with a focus on addressing research gaps in the current and next phases of treaty implementation.