An internal combustion engine (1), including a cylinder head (2) and a cylinder block (3), with a crankcase (10) being fixed to the cylinder block (3), and with at least one mass balancing shaft (20) being held in the crankcase (10). In order to reduce the production effort it is provided that—when seen in the direction of the axis (19a) of the crankshaft (19)—a first pin (26) which is arranged in a borehole (6) and arranged as an alignment pin is positioned in the region of the face side (5) of the crankcase (10) on a straight connecting line (27) between the axis (20a) of the mass balancing shaft (20) and the axis (19a) of the crankshaft (19), with preferably the first pin (26) being arranged in the crankcase (10) and the borehole (6) in the flanged bush (24).