To provide an internal combustion engine capable of variably establishing generation timing and intensity of squish for each engine speed.

This internal combustion engine 1 is provided with a projection 5 provided to project upward from an upper surface of a piston 2 and a recess 7 provided on a cylinder head 6 side to correspond to the projection. The engine is constructed such that the projection quantity of the projection is variable according to speed of the internal combustion engine. Projection quantity of the projection is made relatively small when speed of the internal combustion engine is high.