The mission of the ‘Integrated ocean carbon research’ (IOC-R) programme is to enhance our understanding of the ocean as a changing sink for human-produced CO2 and its climate change mitigation capacity, as well as the vulnerability of ocean ecosystems to increasing CO2 levels. The IOC-R programme aims to provide an actionable foundation for addressing the challenges of ocean carbon research. In doing so, it is contributing to the objectives of the UN Decade of Ocean Science for Sustainable Development by integrating the latest scientific findings and observational data for ocean carbon. This IOC-R report is a global community effort with 71 co-authors and 12 reviewers from 22 countries. The IOC-R programme itself is co-sponsored by five international research and coordination programmes which have a strong involvement and focus on ocean carbon (Global Carbon Project, SOLAS, IMBeR, CLIVAR, IOCCP) and the Intergovernmental Oceanographic Commission of UNESCO (IOC). IOC-R aims to guide the scientific focus of these programmes, as well as the Global Ocean Observing System (co-sponsored by the IOC, World Meteorological Organisation, the United Nations Environment Program and the International Science Council) at large, by identifying knowledge gaps and coordinated research approaches to increase understanding about the ocean carbon cycle in a changing world. It also aims to highlight new global cross-cutting priorities of ocean carbon research helping national and international ocean science funding mechanisms in determining future areas of investment.