The Global City Indicators Program (GCIP) is a decentralized, city-led initiative that enables cities to measure, report, and improve their performance and quality of life, facilitate capacity building, and share best practices through an easy-to-use web portal. Managing cities effectively is critical and becoming more complex as population growth and economic development are taking place in urban areas. Today's big challenges, such as poverty reduction, economic development, climate change, and the creation and maintenance of an inclusive and peaceful society, will all need to be met through the responses of cities. So too will the day-to-day challenges of garbage collection, responding to the house on fire and larger disasters, and facilitating the provision of water, electricity, education, health care, and the myriad of other services that make life more productive and enjoyable. Standardized indicators are essential in order to measure the performance of cities, capture trends and developments, and support cities in becoming global partners.