Otto cycle internal combustion engine, comprising a cylinder block including at least one cylinder having a longitudinal axis, a piston movable within said cylinder and having a recess open on a head surface of the piston, a head fastened to said cylinder block and having a surface facing the cylinder, three intake valves and two exhaust valves movable along respective rectilinear directions, a combustion chamber delimited at one side by a portion of the surface of the head facing the cylinder and, at the other side, by the surface of said recess of the piston. The directions of motion of the valves are parallel to each other, the surface of the head facing the cylinder is planar and orthogonal to the directions of motion of the valves and the combustion chamber is obtained exclusively in the piston.