Abstract: A piston for internal combustion engines, especially for motors of the Diesel type. On purpose to reduce the heat diffusion from the piston crown to the piston portion where are fitted the sealing piston rings, provision is made of an internal circular groove intended to reduce the thickness of the connection portion between the piston crown and the side portion where are fitted the sealing rings, an external cut tangentially formed in the piston side portion substantially at the connection thereof with the piston crown, i.e. above the grooves of the piston rings, being substituted for the circular groove which is interrupted below the regions of the piston crown provided with any recess which would cause the thickness of the connection portion to be too slight.