The International Polar Year (IPY) 2007–2008, sponsored by the International Council for Science (ICSU) and the World Meteorological Organization (WMO), was an unprecedented two-year programme of international science, education, and outreach that brought together the ideas, energy, and resources of many thousands of participants from more than 60 countries in an interdisciplinary framework. IPY 2007–2008 provides a shining example of ICSU’s role in planning and implementing international science programmes.