A straddled vehicle comprising: a vehicle frame including a head pipe; an internal combustion engine supported on the vehicle frame; a radiator supported on the vehicle frame and arranged forward relative to the internal combustion engine; a support cover arranged sideward of the internal combustion engine; a vehicle part a front cover at least a portion of which is arranged forward of the head pipe; an upper cover at least a portion of which is arranged sideward of the head pipe and upward relative to the radiator; an under cover at least a portion of which is arranged sideward of the head pipe and downward of the upper cover; and an outer cover arranged outward of the support cover and the vehicle part in the vehicle width direction, wherein: a groove portion is formed by at least one of the front cover, the upper cover and the under cover, wherein the groove portion includes a front end portion located upward and forward relative to the radiator and a rear end portion located rearward relative to the front end portion, and wherein the groove portion extends rearward from the front end portion to the rear end portion and is depressed inward in the vehicle width direction; at least a portion of a tubular air passage through which air supplied to the vehicle part passes is formed by the support cover and the outer cover; the front end portion of the groove portion has an opening facing forward as the vehicle is seen from the side; and an air inlet opening that communicates with the air passage is formed in the groove portion and characterised in that the vehicle part is an electronic control unit that controls the internal combustion engine, and the electronic control unit is supported on the support cover and arranged outward in a vehicle width direction relative to the support cover, wherein at least a portion of the electronic control unit overlaps with the internal combustion engine as the vehicle is seen from the side. a vehicle frame including a head pipe; an internal combustion engine supported on the vehicle frame; a radiator supported on the vehicle frame and arranged forward relative to the internal combustion engine; a support cover arranged sideward of the internal combustion engine; a vehicle part a front cover at least a portion of which is arranged forward of the head pipe; an upper cover at least a portion of which is arranged sideward of the head pipe and upward relative to the radiator; an under cover at least a portion of which is arranged sideward of the head pipe and downward of the upper cover; and an outer cover arranged outward of the support cover and the vehicle part in the vehicle width direction, wherein: a groove portion is formed by at least one of the front cover, the upper cover and the under cover, wherein the groove portion includes a front end portion located upward and forward relative to the radiator and a rear end portion located rearward relative to the front end portion, and wherein the groove portion extends rearward from the front end portion to the rear end portion and is depressed inward in the vehicle width direction; at least a portion of a tubular air passage through which air supplied to the vehicle part passes is formed by the support cover and the outer cover; the front end portion of the groove portion has an opening facing forward as the vehicle is seen from the side; and an air inlet opening that communicates with the air passage is formed in the groove portion and characterised in that the vehicle part is an electronic control unit that controls the internal combustion engine, and the electronic control unit is supported on the support cover and arranged outward in a vehicle width direction relative to the support cover, wherein at least a portion of the electronic control unit overlaps with the internal combustion engine as the vehicle is seen from the side. a groove portion is formed by at least one of the front cover, the upper cover and the under cover, wherein the groove portion includes a front end portion located upward and forward relative to the radiator and a rear end portion located rearward relative to the front end portion, and wherein the groove portion extends rearward from the front end portion to the rear end portion and is depressed inward in the vehicle width direction; at least a portion of a tubular air passage through which air supplied to the vehicle part passes is formed by the support cover and the outer cover; the front end portion of the groove portion has an opening facing forward as the vehicle is seen from the side; and an air inlet opening that communicates with the air passage is formed in the groove portion and characterised in that the vehicle part is an electronic control unit that controls the internal combustion engine, and the electronic control unit is supported on the support cover and arranged outward in a vehicle width direction relative to the support cover, wherein at least a portion of the electronic control unit overlaps with the internal combustion engine as the vehicle is seen from the side.