CodeX is an HL7 FHIR Accelerator. There are many barriers to collecting and sharing valuable cancer data, including the inconsistent use or absence of data standards and the difficulty of transforming how we receive, access, and share patient information in a complex and non-interoperable healthcare system. Every interaction between a clinician and a cancer patient has the potential to provide data that could be used to improve care for that particular patient, as well as for all who follow. Leveraging the mCODE™ FHIR Implementation Guide standard (minimal Common Oncology Data Elements), HL7 CodeX will expand around this core to address new use cases and accelerate opportunities to create a learning health system based on interoperable data and improved patient care. HL7 CodeX is a community of patients, providers and health systems, researchers, regulators, payers, electronic health record vendors and information technology innovators, and more working to: (1) Revolutionize cancer patient data collection, sharing, and care (2) Empower electronic health record (EHR) and other systems to share cancer data based on mCODE and extensions in an interoperable way and (3) Streamline data collection and sharing to unburden workflows, while protecting patient privacy.