Oscillating piston engine having a polygonal piston, a housing which has the same shape as the piston and is regularly polygonal in axial section of the interior, characterized in that - it has a main shaft, on which a sun gear is firmly seated and in turn drives three satellite gears, on each of which a crankshaft is seated, which sets the piston in a circularly oscillating movement with parallel guidance about the main shaft, and which main shaft represents the output shaft of the oscillating piston engine, - the polygonal interior of the housing is functionally divided into six combustion chambers, i.e. into a first combustion chamber, a second combustion chamber, a third combustion chamber, a fourth combustion chamber, a fifth combustion chamber and a sixth combustion chamber, - an inlet opening and an outlet opening are provided for each combustion chamber, i.e. a first inlet opening and a first outlet opening for the first combustion chamber, a second inlet opening and a second outlet opening for the second combustion chamber, a third inlet opening and a third outlet opening for the third combustion chamber, a fourth inlet opening and a fourth outlet opening for the fourth combustion chamber, a fifth inlet opening and a fifth outlet opening for the fifth combustion chamber, and a sixth inlet opening and a sixth outlet opening for the sixth combustion chamber, - three mutually crossing double wings with partial wings are present, which are each slidably displaceable longitudinally in matching radial grooves of the piston, and which seal the polygonal interior of the housing in the tangential direction by means of sealing strips, wherein the two partial wings of one of the double wings are each connected by substantially radially extending rods (15a, 17a, 19a), - the piston in each combustion chamber guides a sealing strip in a tangentially circumferential groove which seals the combustion chamber radially inwards, and - a shell-shaped compensating mass is present and surrounds the driving part of the engine and is movable by three eccentric discs which are set up such that they are capable of compensating eccentricity of the piston statically and dynamically in any position of the piston. - it has a main shaft, on which a sun gear is firmly seated and in turn drives three satellite gears, on each of which a crankshaft is seated, which sets the piston in a circularly oscillating movement with parallel guidance about the main shaft, and which main shaft represents the output shaft of the oscillating piston engine, - the polygonal interior of the housing is functionally divided into six combustion chambers, i.e. into a first combustion chamber, a second combustion chamber, a third combustion chamber, a fourth combustion chamber, a fifth combustion chamber and a sixth combustion chamber, - an inlet opening and an outlet opening are provided for each combustion chamber, i.e. a first inlet opening and a first outlet opening for the first combustion chamber, a second inlet opening and a second outlet opening for the second combustion chamber, a third inlet opening and a third outlet opening for the third combustion chamber, a fourth inlet opening and a fourth outlet opening for the fourth combustion chamber, a fifth inlet opening and a fifth outlet opening for the fifth combustion chamber, and a sixth inlet opening and a sixth outlet opening for the sixth combustion chamber, - three mutually crossing double wings with partial wings are present, which are each slidably displaceable longitudinally in matching radial grooves of the piston, and which seal the polygonal interior of the housing in the tangential direction by means of sealing strips, wherein the two partial wings of one of the double wings are each connected by substantially radially extending rods (15a, 17a, 19a), - the piston in each combustion chamber guides a sealing strip in a tangentially circumferential groove which seals the combustion chamber radially inwards, and - a shell-shaped compensating mass is present and surrounds the driving part of the engine and is movable by three eccentric discs which are set up such that they are capable of compensating eccentricity of the piston statically and dynamically in any position of the piston.