To describe the background, methodology, and results of the congressionally mandated Department of Veterans Affairs (VA) Traumatic Brain Injury (TBI) Veterans Health Registry. Veterans Health Administration (VHA) and Veterans Benefit Administration (VBA). A total of 441 639 Veterans of post-9/11 conflicts who exhibited symptoms associated with TBI and sought care or benefits from the VA between September 2001 and September 2021. Design: Retrospective analysis of VHA and VBA administrative records. (1) VA/Department of Defense Identity Repository to identify Veterans with a deployment to the Southwest Asia theater of operations; (2) the VA TBI Screening and Evaluation Program data; (3) Inpatient and Outpatient Encounter data; and (4) an extract of the VBA Corporate Database to identify Veterans filing benefit claims based on TBI. An unduplicated total of 441 639 post-9/11 Veterans were identified in the Registry via three different pathways to entry: 369 909 Veterans through a positive TBI Screen, 253 177 Veterans receiving healthcare including a TBI diagnosis, and 108 541 Veterans filing TBI disability claims. Among Veterans reporting current TBI symptoms who completed a clinical evaluation, a diagnosis of TBI was confirmed by a TBI specialist in 68.7% of the cases. The TBI severity of confirmed cases was classified as mild in 86.6% of the cases, moderate in 8.3%, and severe in 4.1%. The TBI Registry Veterans were hospitalized 66 503 times and seen 1 521 898 times as outpatients in VHA facilities with diagnoses including TBI. Among Veterans filing TBI disability claims, 67.3% were adjudicated as service-connected. The VA TBI Health Registry has identified over 440 000 Veterans of post-9/11 conflicts who presented to the VA for care or benefits with TBI symptomatology. This large number and the volume of TBI health care and benefits provided over the two decades since 9/11 demonstrate the need for the VA's strong ongoing focus on screening, evaluation, and rehabilitation of TBI. Key words:Department of Veterans Affairs, post-9/11, Registry, TBI, traumatic brain injury, VA, VBA, Veterans, Veterans Benefit Administration, Veterans Health Administration, VHA.