For the first time in human history, the majority of the world’s population now lives in cities. Global investment in urban infrastructure is on the rise and increasingly, cities are feeling accountable for the health and well-being of their populations. The motivation for this accountability is simple – poor population health can be a substantial drain on a city’s resources and as cities compete with each other, having a healthy population can be a substantial advantage. The Healthy Cities Initiative at Harvard Global Health Institute is partnering with organizations around the globe to facilitate targeted research on the relationship between health and urban infrastructure, and to engage in both education and policy translation to ensure that knowledge about how to make cities healthier is spread more widely. The Initiative will bring together scholars across a multitude of fields, along with senior policy makers to share best practices and lessons learned, build collaborations between cities, and develop working groups who tackle the pressing challenges facing cities.