This article describes an explosion in the availability of individual-level public administrative data in the United States and worldwide. These datasets can be used as stand-alone resources or linked across different sources. These new resources will facilitate transformative research on social, demographic, and economic changes, policy evaluation, and other experimental analyses. We discuss the current status of administrative big data in the United States, their potential to advance social science and policy studies, and advantages and challenges for using these data in practice. We showcase a few ongoing large-scale U.S. administrative data initiatives and hope to spark future parallel endeavors in other countries.