Alcohol dehydrogenase 1A is an enzyme that in humans is encoded by the ADH1A gene.

This gene encodes class I alcohol dehydrogenase, alpha subunit, which is a member of the alcohol dehydrogenase family. Members of this enzyme family metabolize a wide variety of substrates, including ethanol, retinol, other aliphatic alcohols, hydroxysteroids, and lipid peroxidation products. Class I alcohol dehydrogenase, consisting of several homo- and heterodimers of alpha, beta, and gamma subunits, exhibits high activity for ethanol oxidation and plays a major role in ethanol catabolism. Three genes encoding alpha, beta and gamma subunits are tandemly organized in a genomic segment as a gene cluster. This gene is monomorphic and predominant in fetal and infant livers, whereas the genes encoding beta and gamma subunits are polymorphic and strongly expressed in adult livers.