A drive unit for oscillatingly driven mowing sickles has a first transmission unit {1} with a first housing (5) defining a first axis (6). A rotor (7) is rotationally supported in the first housing (5) around the first axis (6). A first internal gear wheel (10) is fixed in the first housing (5) and provided with internal teeth. A toothed pinion (14) is rotationally supported in the rotor (7) around a second axis (12). The second axis (12) is radially off-set to the first axis (6). The toothed pinion (14) forms the output element of the drive unit and meshes with the first internal gear wheel (10). A second transmission unit (2) has an output (34) non-rotationally connected to the rotor (7) of the first transmission unit (1). The second transmission unit (2) is formed as a step-down gear. A motor (4), with an output shaft (45), rotationally drives the second transmission unit (2). The rotational speed N1 is reduced by the second transmission unit (2), formed as a step-down gear, to the rotational driving speed N2 of the first transmission unit (1).