Disclosed is a compound harmonic drive including: an inner ring gear including a first set of gear teeth; a flex spline including a flex spline inner ring and a flex spline outer ring, the flex spline inner ring forms a second set of gear teeth that engage the first set of gear teeth and the flex spline outer ring forms a third set of gear teeth; an outer ring gear including a fourth set of gear teeth that are engaged by the third set of gear teeth; and a wave generator disposed between the flex spline inner ring and the flex spline outer ring, wherein the gear system rotates about an axis and each set of gear teeth is axially aligned with each other and radially offset from each other about the axis.