Investments in early childhood care and education (ECCE) have contributed to a growing demand for internationally comparable data. Yet data on access to quality ECCE are not routinely collected in many countries, leading to limited information on equitable access to ECCE, quality of provision, and the impact on learning and wellbeing outcomes. This paper outlines the current status of global measurement of access to quality ECCE and identifies issues with definitions, availability, and accuracy of ECCE data across countries and outlines paths forward. We argue that estimates of access to ECCE should be based on children's participation in quality ECCE across multiple program types, rather than enrollment or attendance alone, given the critical importance of dosage and participation for ensuring positive benefits from ECCE. Governments, international organizations, and researchers all have roles to play in setting standards to define and monitor ECCE, generating workable tools for measuring nationally, and globally investing in national monitoring systems and routine household surveys to obtain accurate estimates of access to quality ECCE. [This manuscript was developed through the UKRI GCRF Harnessing the power of global data to support young children's learning and development research group.]