A modular fuel cell system is provided, especially for use in vehicles, with a fuel cell module, which has a stack of a plurality fuel cell elements between a first end plate and a second end plate, with a burner-heat exchanger module, which has a heat exchanger for preheating cathode gas and a burner for reacting fuel cell waste gases. Manufacturing advantages are provided with the first end plate has, on a connection side facing away from the stack, an anode gas inlet opening, a cathode gas inlet opening, an anode waste gas outlet opening and a cathode waste gas outlet opening and if the burner-heat exchanger module has an anode gas outlet opening communicatingly connected to the an anode gas inlet opening, an cathode gas outlet opening communicatingly connected to the an cathode gas inlet opening, an anode waste gas inlet opening communicatingly connected to the an anode waste gas outlet opening and an cathode waste gas inlet opening communicatingly connected to the an cathode waste gas outlet opening.