Open Educational Resources (OER) — teaching, learning and research materials that their owners make free for others to use, revise and share — offer a powerful means of expanding the reach and effectiveness of worldwide education. The Commonwealth of Learning (COL) and UNESCO co-organised the World OER Congress in 2012 in Paris. That Congress resulted in the OER Paris Declaration: a statement that urged governments around the world to release, as OER, all teaching, learning and research materials developed with public funds. This book, drawing on 15 case studies contributed by 29 OER researchers and policy-makers from 15 countries across six continents, examines the implementation of the pivotal declaration through the thematic lenses of policy, costs and transformation. The case studies provide a detailed picture of OER policies and initiatives as they are unfolding in different country contexts and adopting a range of approaches, from bottom-up to top-down. The book illuminates the impacts of OER on the costs of producing, distributing and providing access to learning materials, and shows the way that OER can transform the teaching and learning methodology mindset. Recommendations on key actions to be taken by policy-makers, practitioners, OER developers and users are also outlined, particularly within the context of Education 2030. Clearly, progress is being made, although more work must be done if the international community is to realise the full potential of OER.