Despite advances in treatment, uncontrolled myasthenia gravis (MG) remains a clinical challenge associated with increased mortality. This study aimed to evaluate the mortality risk in patients with uncontrolled MG compared with those with controlled MG. A retrospective cohort study was conducted using South Korea’s nationwide claims database between January 1, 2007, and February 28, 2023. Patients newly diagnosed with MG between 2008 and 2020 were classified into uncontrolled MG (n=58) and controlled MG (n=9,486) groups based on the use of corticosteroid dose, non-steroidal immunosuppressants, and intravenous immunoglobulin/plasma exchange administration. We estimated hazard ratios (HR) and 95% confidence intervals (CI) of all-cause mortality using Cox proportional hazards models. The mortality risk was significantly higher in patients with uncontrolled MG compared to patients with controlled MG (incidence rates: 4.0 vs. 2.0 per 100 person-years, respectively; adjusted HR: 2.12, 95% CI: 1.19?3.76). Kaplan- Meier survival curves confirmed reduced survival probabilities in uncontrolled MG patients over time. Our study found the significant mortality burden associated with uncontrolled MG and the importance of achieving sustained disease control. Further efforts are needed to opti...