Fuel injector

The fuel injector comprises a housing formed of at least a nozzle retaining nut (DS), a first injector module (I1), and a second injector module (I2). The first injector module (I1) and the second injector module (I2) are adjacent to one another and are arranged in the nozzle retaining nut (DS). A high-pressure bore (H) for fuel is conducted through the first injector module (I1) and the second injector module (I2). A return bore (R) for fuel is arranged in the housing. Contact surfaces between the injector modules (I1, I2) form a first gap (S1) which is adjacent to the high-pressure bore (H). Contact surfaces between the nozzle retaining nut (DS) and the injector modules (I1, I2) form a second gap (S2) which is connected to the first gap (S1). To remove fuel that has leaked from the high-pressure bore (H) via the first gap (S1) into the second gap (S2), the return line (R) is adjacent to the second gap (S2). The fuel injector is configured such that the second gap (S2) is sealed against the surroundings of the fuel injector.