Focusing on the Large Marine Ecosystems (LMEs) of the world, this course will introduce the concept and practice of ecosystem-based management. LMEs occupy areas of coastal ocean at least 200 000 km² or greater in size. These coastal waters produce 12.6 trillion USD in ecosystem goods and services annually and are vitally important for billions of people around the globe. Because LMEs are bounded by ocean features and are globally linked, management of human activities needs to occur in an integrated fashion across political boundaries and economic sectors (e.g. fishing, shipping, energy, tourism, and mining.) This represents a new type of management approached - shifting from single sector-based to multi-sector assessment and management within the spatial domain of the world's 66 Large Marine Ecosystems. There is global high-level support for this new approach and in this course, we will introduce the concepts and tools for assessing and managing LMEs. Together, leaders and experts in a global movement to recover and sustain the goods and services of LMEs will introduce you to the mechanisms used for assessment (Transboundary Diagnostic Analysis), planning and implementation (Strategic Action Programme). Based on recent activities in implementation and practice of the LME approach in 22 projects around the globe, we will showcase examples of effective management at this scale, and highlight the challenges and issues. By the end of the online course, we hope you will be able to actively use this knowledge to advance sustainable development of the world’s oceans. The course was created with the support and input of: the Global Environment Facility (GEF), the United Nations Development Program (UNDP), the National Oceanic and Atmospheric Administration (NOAA), UNESCO-IOC and IW:LEARN.