Background: Relationships between health insurance coverage and radiotherapy (RT) interruption rates in patients with head and neck (H&N) cancer remain unclear. Methods: We performed a retrospective cohort study at our academic center. Days of RT interruption for individual patients were tabulated, analyzed for explanatory variables, and geographically mapped. Results: 894 of 7526 (11.9%) scheduled treatment days were interrupted, impacting 149 of 216 (69%) patients. Medicaid/uninsured patients experienced a 7.3 day mean interruption (SD = 9.9) vs 3.4 days (SD = 5.2) for Medicare/private patients (P <.001). RT interruption was predicted by insurance status in multivariate analysis (P =.008). Higher RT interruption rates overlapped geospatially with low predicted median household income and racial minority neighborhoods. Conclusion: Unplanned treatment interruptions are a key source for H&N RT quality shortfalls in Medicaid/uninsured patients. This is the first geographic benchmarking of H&N RT delivery disparities across a complete metropolitan region, and will guide interventions studies to reduce interruption risk.