An internal combustion engine for a straddled vehicle, comprising: a cylinder including a cylinder wall demarcating a cylinder bore; a piston accommodated in the cylinder bore, the piston reciprocally movable in a first direction and in a second direction opposite to the first direction, the first direction being parallel to a cylinder axial line; and a cylinder head provided at an end of the cylinder bore, toward which the first direction is directed, the cylinder head demarcating a combustion chamber together with the cylinder wall and the piston; wherein: the piston includes: a piston head demarcating an end of the combustion chamber, toward which the second direction is directed; a piston ring (43a, 43b, 43c) attached to an outer circumference of the piston head, the piston ring (43a, 43b, 43c) including an outer circumference coming into contact with the cylinder wall to transmit heat of the piston to the cylinder wall; and a piston skirt including a slidable portion (sp) slidable against the cylinder wall, the piston skirt extending in the second direction along the cylinder wall from the outer circumference of the piston head; the piston ring (43a, 43b, 43c) includes a diamond-like carbon layer on the outer circumference thereof; and characterized in that the slidable portion (sp) of the piston skirt includes a resin layer in at least a part thereof, the resin layer preventing the heat of the piston from being transmitted from the piston skirt to the cylinder wall. a cylinder including a cylinder wall demarcating a cylinder bore; a piston accommodated in the cylinder bore, the piston reciprocally movable in a first direction and in a second direction opposite to the first direction, the first direction being parallel to a cylinder axial line; and a cylinder head provided at an end of the cylinder bore, toward which the first direction is directed, the cylinder head demarcating a combustion chamber together with the cylinder wall and the piston; the piston includes: a piston head demarcating an end of the combustion chamber, toward which the second direction is directed; a piston ring (43a, 43b, 43c) attached to an outer circumference of the piston head, the piston ring (43a, 43b, 43c) including an outer circumference coming into contact with the cylinder wall to transmit heat of the piston to the cylinder wall; and a piston skirt including a slidable portion (sp) slidable against the cylinder wall, the piston skirt extending in the second direction along the cylinder wall from the outer circumference of the piston head; a piston head demarcating an end of the combustion chamber, toward which the second direction is directed; a piston ring (43a, 43b, 43c) attached to an outer circumference of the piston head, the piston ring (43a, 43b, 43c) including an outer circumference coming into contact with the cylinder wall to transmit heat of the piston to the cylinder wall; and a piston skirt including a slidable portion (sp) slidable against the cylinder wall, the piston skirt extending in the second direction along the cylinder wall from the outer circumference of the piston head; the piston ring (43a, 43b, 43c) includes a diamond-like carbon layer on the outer circumference thereof; and characterized in that the slidable portion (sp) of the piston skirt includes a resin layer in at least a part thereof, the resin layer preventing the heat of the piston from being transmitted from the piston skirt to the cylinder wall.