The oceans are a significant source of protein, economy and culture for billions of people around the world. Three-quarters of the world’s mega-cities are by the sea and 40% of the global population lives within 100 km of the coast. Marine waters contain some of the most biologically diverse ecosystems on the planet, and a healthy ocean is essential for our survival and wellbeing. Human activities that affect ocean health are growing rapidly in variety, intensity, and impact. There is increasing development pressure in coastal waters for aquaculture, tourism and renewable energy, and there are both on-going and new stressors and threats to all parts of the ocean from land-based pollution, overfishing, other forms of extraction, and climate change. Existing management systems are insufficient to address the increasing impacts and to balance multiple planning objectives across sectors. New management approaches are essential for ensuring that coastal communities and the world’s ocean nations will continue to reap long-term benefits that healthy oceans can provide.