An internal combustion engine includes: a cylinder head (3); a combustion chamber recess (15) formed in the cylinder head; an intake passage (16) and an exhaust passage (17) formed in the cylinder head and communicating with the combustion chamber recess; a head oil passage (80) formed in the cylinder head, and having a first end (81A) communicating with an oil pump (62) and a second end (81B) opening out at a sliding contact surface of a valve actuating mechanism (23) provided in the cylinder head; and an oil jacket (84) formed in the cylinder head in a path of the head oil passage so as to at least partly surround the exhaust passage.