<p>Electrical control of magnetization in nanoscale devices can be significantly improved through the efficient generation of orbital currents and their conversion into spin currents. In nonmagnetic/ferromagnetic bilayers, this conversion produces a torque on the magnetization, enabling magnetization switching and dynamic manipulation. While previous studies focus on metallic ferromagnets, we demonstrate a large orbital torque and enhanced orbital-to-spin conversion by an antiferromagnetic insulating CoO layer. Measurements in CuO_x/CoO/Co trilayers show that inserting CoO reverses the torque’s sign and triples its magnitude compared to CuO_x/Co. This behaviour stems from the inverted oxygen gradient at the CuO_x/CoO interface and CoO’s high orbital multiplicity, which favours the transmission of orbital momenta and efficient orbital-to-spin conversion. At low temperatures, the onset of antiferromagnetic order induces a further many-fold increase of the torque, which we attribute to the efficient excitation and propagation of spin-orbit excitons induced by magnetic coupling. Comparative measurements of CuO_x/NiO/Co and CuO_x/MnO/Co trilayers show that the torque efficiency scales with the orbital momentum of the Co²⁺, Ni²⁺, and Mn²⁺ ions in the antiferromagnet. These results reveal that antiferromagnetic insulators like CoO provide highly effective orbital-to-spin transduction, combining orbital torque and exchange bias functionalities to improve the performance of spintronic devices.</p>