Abstract: A combustion chamber, designed for compression ignition internal combustion engines, solves the problem of distribution and whirling of fuel mixture in the combustion chamber of the engine and from this the resulting easier ignition of fuel mixture, optimum increase in the combustion pressures with optimum layout of the valve gear and the intake and exhaust channels in a simplified design of the cylinder head enabled by the larger eccentricity of the injection jet. A rotary combustion chamber is formed in the piston head, the bottom of the chamber formed by a rotary peripheral surface and rotary internal surface with a circular barrier. Ratios between the depth of the rotary peripheral surface and the depth of the top of the barrier, the largest diameter of the rotary internal surface and the largest diameter of the rotary peripheral surface, and the depth of both rotary surfaces are defined in specific ranges.