A fuel-cell system, particularly a fuel-cell system for a drive system of a motor vehicle, includes an autothermic reformer unit configured to generate hydrogen from a raw material. The hydrogen is used to operate a fuel-cell unit disposed downstream of the reformer unit. An oxidation device configured to convert carbon monoxide into carbon dioxide is disposed between the reformer unit and the fuel cell unit. A water injection device is disposed in the oxidation device and is configured to inject water into the oxidation device.