Background: Demyelinating disorders are a group of chronic immune-mediated diseases affecting myelinated axons in the central nervous system, which lead to life-long disability. In Mongolia, the last regional prevalence study was conduct ed in 2010. Our study objective is to describe the current prevalence of multiple sclerosis (MS) and other demyelinating disorders in Mongolia. : Aim Materials and Methods: We registered MS, neuromyelitis optica spectrum disease (NMOSD), myelin oligodendrocyte glycoprotein (MOG), and acute disseminated encephalomyelitis (ADEM) cases diagnosed according to the 2017 McDon ald criteria, the 2023 NMOSD diagnostic criteria, International MOGAD Panel proposed criteria. Results: The study was conducted in all tertiary, 7 regional, and 20 provincial hospitals across Mongolia and has collected comprehensive data on 965 patients. The prevalence of total demyelinating disorders was estimated to be 27.2, MS 15.6, NMOSD 5.6, MOG 0.06, and ADEM 0.9 per 100,000 total population, respectively. The prevalence of demyelinating disorders between provinces was compared in order of geographical latitude, from lowest to highest, and was statistically significant. Latitude is associated strongly with the prevalence of demyelinating disorders (p=0.006, 95% CI 14.3-22.4, Pearson correlation=0.603) and moderately with the prevalence of MS (p=0.028, 95% CI 9.39-15.6, Pearson correla tion=0.503). Conclusion In Mongolia, the prevalence of MS has significantly increased and can be considered at medium risk, but still much lower than that in Western countries. The prevalence of NMOSD is almost similar to other Asian countries. An obvious latitude gradient for demyelinating disorders was observed in the Mongolian population.