Abstract: The invention relates to a rotary drive assembly for a drill rod having an outer tube and an inner rod extending at least in sections inside the outer tube, comprising a first gear unit having at least a first drive unit for driving the inner rod in a rotating manner and a second gear unit, which is offset to the said first gear unit in the longitudinal direction of the drill rod and has at least a second drive unit for driving the outer tube in a rotating manner. In accordance with the invention provision is made for the second drive unit to be spaced from the second gear unit and for the second drive unit to be arranged adjacent to the first drive unit on the first gear unit.