Abstract <p>This article examines the kinetics of aluminum oxidation in sub- and supercritical water, which is of significant scientific and practical interest for producing functional oxide materials. Oxidation tests of aluminum samples in a high-pressure reactor at temperatures of 325, 350, and 375°C, followed by analysis of the mass of unreacted metal and the volume of remaining water, were experimentally carried out For mathematical modeling of the process kinetics, the Runge–Kutta–Merson method in MS Excel was used, along with macros for constructing and solving systems of differential equations based on stoichiometric matrices. A kinetic model was proposed and gradually refined, accounting for the heterogeneous nature of the process, including the stages of aluminum activation due to oxide film breakdown, the oxidation reaction itself with the formation of boehmite (2Al + 4H₂O → 2AlOOH + 3H₂), and the water splitting reaction (2H₂O → O₂ + 2H₂) near the critical point. The most adequate model was described by a system of six differential equations, which considered both the chemical stages and diffusion limitations.</p>