A harmonic buckling actuator includes buckling units engaged to a rotational track/gear. Each buckling unit includes two input actuators. One end of each input actuator is constrained to rotate about a rotational joint that is rigidly attached to a common ground. The other end of each input actuator is constrained to move with the other actuator of the same buckling unit along a single output axis via another rotational joint that is the output of the buckling unit. The inactivated, unforced configuration of each buckling unit is such that the input actuators are nearly collinear with the line segment connecting the unit's grounded rotational joints. The buckling units are arrayed around the track/gear such that their outputs are spatially phased within the groves of the track/gear. Harmonic activation of the buckling units generates torque on the track/gear about its output axis.