BACKGROUND AND OBJECTIVES: Association of human leukocyte antigen (HLA) with anti-aquaporin-4 immunoglobulin G-positive neuromyelitis optica spectrum disorder (AQP4-IgG NMOSD) has been reported. However, this association in the Korean population has not been previously investigated. We aimed to evaluate whether specific HLA subtypes were associated with Korean patients with AQP4-IgG NMOSD and whether the HLA genotype is associated with specific clinical features. METHODS: We compared the HLA subtypes of 122 patients with AQP4-IgG NMOSD with those of 485 (HLA-A, HLA-B, HLA-C, HLA-DRB1, and HLA-DQB1) and 173 (HLA-DPB1) healthy controls. In addition, we compared the clinical features of patients with and without specific HLA genotypes. RESULTS: The most significant risk allele for AQP4-IgG NMOSD was HLA-DRB1*03:01 (24 patients [19.67%], odds ratio [OR]: 3.997, DISCUSSION: In a Korean cohort of patients withAQP4-IgG NMOSD, the HLA-DRB1*12:02-DQB1*03:01 haplotype was associated with disease severity at onset. HLA-DRB1*03:01, broadly reported as a significant susceptibility allele across diverse ethnic groups, showed a significant risk association in Korean patients with AQP4-IgG NMOSD.