Abstract: An internal combustion engine has an annular rotor (2) arranged to rotate around a stator (6). The stator has a pair of combustion cylinders (19) extending therethrough with each cylinder containing a slideable piston (18). The pistons are coupled to a central rotating shaft (4) which produces antiphase motion of the pistons in their respective cylinders. Combustible fluid is fed into each of the cylinders (19) in turn to be compressed by the action of the pistons (18). The rotor (2) has a first angular section (16) which provides for an air/fuel mixture to be drawn into the cylinders during retraction of the pistons, a second angular section (40) which provides for sealing an opening in the end of the cylinders when the pistons are extending to compress the air/fuel mixture, and a third angular section (42) which has a number of turbine blades which are arranged to be driven by combustion products exiting from a cylinder when compressed fluid therein is ignited.