An air supply installation for a motor vehicle with an airflow passage connecting the air inlet with an air outlet, in which, viewed in the direction of flow, a water separator and an air filter are disposed behind each other. To obtain good separation of the water along with little noise generation, the water separator is embodied as an essentially vertically extending perforated wall, whose perforation holes respectively penetrate the wall with hole axes which are essentially parallel with each other, into which tubes have been inserted which preferably project from both sides of the wall. The air filter is disposed at only a short distance from the water separator and parallel therewith or inclined under an acute angle.