VARIABLE-COMPRESSION-RATIO INTERNAL COMBUSTION ENGINE

An upper oil pan assembly is attached to the lower portion of a cylinder block. An opening is formed on a side wall of the upper oil pan assembly. The variable compression ratio mechanism changes a top dead center position of a piston in accordance with the rotational position of a control shaft to thereby change the compression ratio. The control shaft is rotationally driven by an actuator. At least a portion of the actuator is fixed to a main bearing cap in a state in which at least a portion thereof is positioned on the outer side of an upper oil pan assembly.