HLA-A23 (A23) is a human leukocyte antigen serotype within HLA-A serotype group. The serotype is determined by the antibody recognition of α23 subset of HLA-A α-chains. For A23, the alpha, "A", chain are encoded by the HLA-A*23 allele group and the β-chain are encoded by B2M locus. This group currently is dominated by A*2301. A23 and A*23 are almost synonymous in meaning. A23 is a split antigen of the broad antigen HLA-A9 and it is a sister serotype of HLA-A24.
A23 is common in Africa and regions of the Middle East, Mediterranean, and India than Europe, East Asia or the Americas.