The internal combustion engine piston has an integral combustion chamber defined by a lateral surface originating from the upper surface of the piston. The chamber (5) has a bottom surface (7) blending with the lateral surface. The chamber has two cavities, each located in a first plane containing the axis of the chamber and which is parallel to the axes of the piston pin seats and on the opposite side of the axis wr.t.t. the other cavity. Each cavity is defined by a surface blending with the upper surface of the piston and the lateral surface of the chamber.
