A fuel cell system mounted in a vehicle includes a fuel cell, a collision prediction device, a discharge device, and a controller. The fuel cell includes a gas channel to which a reactant gas is to be supplied to generate electricity. The collision prediction device is configured to predict probability of collision of the vehicle. The discharge device is configured to discharge the electricity from the fuel cell. The controller is configured to control the discharge device to discharge the electricity from the fuel cell in a case where the collision prediction device predicts that the probability of collision of the vehicle is higher than a predetermined probability.