An arc-heated wind tunnel is a ground-based facility for generating a flow with a high temperature and high Mach number by arc discharge and supersonic expansion. The basic components of the facility are the inlet, constrictor (discharge), and nozzle (expansion) sections. Applications include reproduction of the planet-entry environment and performance tests and development of thermal protection systems, such as ablators and heat resistance ceramics. To perform such experiments with high-quality data, the physical properties of the free jet discharged from the nozzle exit must be understood. In an arc-heated wind tunnel, however, the flow field is very complicated because of the complex phenomena of the heating process in the constrictor and the strong thermochemical nonequilibrium in the nozzle. This entry presents specific types of arc-heated wind tunnels, e.g., constrictor, segmented, and Huels. Important phenomena of the arc-heated flow such as ionization, thermochemical nonequilibrium, radiation, and turbulence are explained. Remarkable developments in high-performance computers have meant that the numerical simulation technique has become an effective method for diagnosing the distribution of arc-heated flow properties. This entry describes and reviews analysis models of the plasma flow in an arc-heated wind tunnel, including several nonequilibrium, radiation, and turbulence models. A formulation for plasma flow simulation in an arc-heated wind tunnel is introduced, and analysis results for the flow properties in different types of arc heaters are presented.