Apparatus for varying a compression ratio of a reciprocating piston internal combustion engine, - with an externally toothed eccentric which is arranged in a rotationally movable manner between a crankpin journal of a crankshaft of a crank drive of the reciprocating piston internal combustion engine and a connecting rod eye of the connecting rod of the reciprocating piston internal combustion engine in order to vary a stroke height of the piston, coupled mechanically to the connecting rod, of the reciprocating piston internal combustion engine, - with an adjusting unit which is mechanically coupled indirectly to an external toothing system of the eccentric, and is configured to set the eccentric by way of rotation of the eccentric, and - the coupling unit which is configured to mechanically couple the eccentric to the adjusting unit, wherein: - the coupling unit is configured with first and second take-off shafts (5, 6) which are arranged parallel to one another, are spaced apart from one another radially, and are coupled mechanically to one another, - the first take-off shaft is coupled mechanically to the external toothing system of the eccentric, - the second take-off shaft is coupled mechanically to the adjusting unit, - the coupling unit with the first and second take-off shafts (5, 6), the eccentric and the adjusting unit are configured partially or completely in the interior of a crankcase of the crankshaft of the reciprocating piston internal combustion engine, an interior space of a web of the crankshaft of the reciprocating piston internal combustion engine, and an installation space of a counterweight of the crankshaft of the reciprocating piston internal combustion engine, - the first take-off shaft of the coupling unit is arranged spaced apart parallel and radially with respect to a rotational axis of the crankshaft of the reciprocating piston internal combustion engine, and has an externally toothed first gearwheel for rotating the eccentric, and a second gearwheel offset axially and fixedly for conjoint rotation with respect to the first gearwheel of the first take-off shaft, and - the second take-off shaft of the coupling unit is arranged spaced apart parallel and radially with respect to the rotational axis of the crankshaft and with respect to the first take-off shaft, and has an externally toothed first gearwheel such that it meshes with the second gearwheel of the first take-off shaft, and has an externally toothed second gearwheel offset axially and fixedly for conjoint rotation with respect to the first gearwheel of the second take-off shaft. - with an externally toothed eccentric which is arranged in a rotationally movable manner between a crankpin journal of a crankshaft of a crank drive of the reciprocating piston internal combustion engine and a connecting rod eye of the connecting rod of the reciprocating piston internal combustion engine in order to vary a stroke height of the piston, coupled mechanically to the connecting rod, of the reciprocating piston internal combustion engine, - with an adjusting unit which is mechanically coupled indirectly to an external toothing system of the eccentric, and is configured to set the eccentric by way of rotation of the eccentric, and - the coupling unit which is configured to mechanically couple the eccentric to the adjusting unit, - the coupling unit is configured with first and second take-off shafts (5, 6) which are arranged parallel to one another, are spaced apart from one another radially, and are coupled mechanically to one another, - the first take-off shaft is coupled mechanically to the external toothing system of the eccentric, - the second take-off shaft is coupled mechanically to the adjusting unit, - the coupling unit with the first and second take-off shafts (5, 6), the eccentric and the adjusting unit are configured partially or completely in the interior of a crankcase of the crankshaft of the reciprocating piston internal combustion engine, an interior space of a web of the crankshaft of the reciprocating piston internal combustion engine, and an installation space of a counterweight of the crankshaft of the reciprocating piston internal combustion engine, - the first take-off shaft of the coupling unit is arranged spaced apart parallel and radially with respect to a rotational axis of the crankshaft of the reciprocating piston internal combustion engine, and has an externally toothed first gearwheel for rotating the eccentric, and a second gearwheel offset axially and fixedly for conjoint rotation with respect to the first gearwheel of the first take-off shaft, and - the second take-off shaft of the coupling unit is arranged spaced apart parallel and radially with respect to the rotational axis of the crankshaft and with respect to the first take-off shaft, and has an externally toothed first gearwheel such that it meshes with the second gearwheel of the first take-off shaft, and has an externally toothed second gearwheel offset axially and fixedly for conjoint rotation with respect to the first gearwheel of the second take-off shaft.