The purpose of this brief is to highlight a range of federal, state, and local administrative data sources that could be used to address policy-relevant ECE questions. We describe data sources across four main areas: early care and education; health; child welfare, public assistance, and human services; and employment. We offer examples of the types of ECE research questions that could be answered when data sources from these areas are linked with other sources (e.g., when various ECE data sources are linked with one another, as well as when ECE data are linked with other data). This resource is not meant to be exhaustive. Rather, it serves as a starting place for researchers or state agency staff interested in understanding the variety of administrative data that could be linked together to answer policy-relevant questions in early care and education. (author abstract)