The invention concerns an internal-combustion engine, the engine comprising a first combustion chamber, a first piston displaceably guided in the first combustion chamber, the first piston facing the first combustion chamber with a first piston surface in a first direction, a second combustion chamber, a second piston displaceably guided in the second combustion chamber, the second piston facing the second combustion chamber with a second piston surface in a second direction, the first direction and the second direction being opposed to each other, the first piston and the second piston being coupled to each other so that they move simultaneously.