Purpose To report long-term outcomes of radiation segmentectomy (RS) for early hepatocellular carcinoma (HCC). The authors hypothesized that outcomes are comparable to curative treatments for patients with solitary HCC less than or equal to 5 cm and preserved liver function. Materials and Methods This retrospective study included 70 patients (median age, 71 years; range, 22-96 years) with solitary HCC less than or equal to 5 cm not amenable to percutaneous ablation who underwent RS (dose of >190 Gy) between 2003 and 2016. Patients who underwent subsequent curative liver transplantation were excluded to eliminate this confounding variable affecting survival. Radiologic response of time to progression and median overall survival were estimated by using the Kaplan-Meier method per the guidelines of the European Association for the Study of the Liver (EASL) and the World Health Organization (WHO). Results Seventy patients were treated with RS over 14 years. Sixty-three patients (90%) showed response by using EASL criteria, of which 41 (59%) showed complete response. Fifty patients (71%) achieved response by using WHO criteria, of which 11 (16%) achieved complete response. Response rates at 6 months were 86% and 49% by using EASL and WHO criteria, respectively. Median time to progression was 2.4 years (95% confidence interval: 2.1, 5.7), with 72% of patients having no target lesion progression at 5 years. Median overall survival was 6.7 years (95% confidence interval: 3.1, 6.7); survival probability at 1, 3, and 5 years was 98%, 66%, and 57%, respectively. Overall survival probability at 1, 3, and 5 years was 100%, 82%, and 75%, respectively, in patients with baseline tumor size less than or equal to 3 cm (n = 45) and was significantly longer than in patients with tumors greater than 3 cm (P = .026). Conclusion RS provides response rates, tumor control, and survival outcomes comparable to curative-intent treatments for selected patients with early-stage HCC who have preserved liver function. ^© RSNA, 2018 Online supplemental material is available for this article.