When Member States of the United Nations approved the 2030 Agenda for Sustainable Development in 2015, they agreed that the Sustainable Development Goals and Targets should be met for all nations and peoples and for all segments of society. Governments and stakeholders negotiating the 2030 Agenda backed the ambition of leaving no one behind, an ambition increasingly referred to in development policies, international agendas and civil society advocacy.How can we transform this ambition into reality? Policy makers, civil society and business are asking for more clarity on how to ensure that no one is left behind in practice. What does it mean for the design and delivery of economic, social and environmental policies? How should development co-operation policies, programming and accountability adapt? What should governments, development partners and the international community do differently to ensure that sustainable development goals benefit everyone and the furthest behind first? The 2018 Development Co-operation Report: Joining Forces to Leave No One Behind addresses all of these questions and many more. Informed by the latest evidence on what it means to be left behind, it adopts a wide range of perspectives and draws lessons from policies, practices and partnerships that work. The report proposes a holistic and innovative framework to shape and guide development co-operation policies and tools that are fit for the purpose of leaving no one behind.