INTRODUCTION/AIMS: Patient registries are valuable tools for outcomes research in rare diseases such as myasthenia gravis (MG). Existing MG registries are limited by factors including a lack of geographical scope. MGBase has been designed as a global, observational registry aimed at studying clinical practice outcomes in MG. METHODS: MGBase was developed with the support of the independent MSBase Foundation. An international scientific leadership group (SLG) established a minimum dataset and outcome measures. Data are entered on a purpose-designed platform in real time and held in a web-based registry. Members can request access to the global dataset for investigator-driven substudies. RESULTS: MGBase data collection commenced in October 2021. From inception until April 2024, 565 patients from 16 clinics and 8 countries were enrolled. The cohort is 56% female, with a mean age of 57 (SD19) years at the last visit and a median disease duration of 5 (IQR 1.8, 10.8) years. Seventy-six percent of patients are acetylcholine receptor antibody positive (AChR ab+) and 7% have antibodies to muscle-specific kinase (MuSK ab+). At diagnosis, 33% of patients had ocular MG. Immunotherapy was used in 87% of patients. A minority of patients (7%) required three or more concurrent immunotherapies. Thymectomy was performed in 24% of patients. DISCUSSION: MGBase is a global registry for collaborative research in MG. Interim analysis of registry data shows disease characteristics similar to those previously published. As global enrollments increase, the registry will generate clinical practice evidence of treatment outcomes, safety, and disease prognostic markers.