To provide an air intake system for a vehicle, so simple in structure as to reduce the cost and effective to increase the ram pressure, a front cowling (19) is mounted on a front portion of a vehicle body structure (1). This front cowling (19) has left and right headlight windows (20 and 21) aligned with left and right headlights (22 and 23), respectively, and also has an air intake opening (24) defined therein at a location above the headlight windows (20 and 21) for introducing an external combustion air (A) towards the vehicle engine (E). An intake air passage (35) is provided for introducing the combustion air (A), then entering the air intake opening (24), towards an air cleaner (30) by way of opposite lateral portions of a head tube (3).