Child marriage is a global problem that cuts across countries, cultures, and religions. Around 650 million women and girls alive today were married as children. Unless we accelerate our efforts, 150 million more girls will be married by 2030. The 17 Sustainable Development Goals (SDGs) set out global development priorities between now and 2030. They are a universal call to action to end poverty, protect the planet and ensure that all people enjoy peace and prosperity, centred on the realisation of human rights. The SDGs include a goal on gender equality and – as a fundamental part of it – a target to end the harmful practice of child marriage by 2030. However, the consequences of not achieving this target reach beyond Goal 5. Unless we make significant progress on ending child marriage, we will fall short on eight of the SDGs, including those related to: poverty, food security, health, education, gender equality, economic growth, and peace and justice.