Investigating the dynamic mechanical behavior of single-crystal aluminum oxynitride (AlON) is fascinating and crucial for understanding material performance in relevant applications. Nevertheless, there is limited exploration into the dynamic mechanical properties of AlON single crystals. In this study, a series of nano-impact experiments (strain rate ) have been performed on the three principal orientations ((010), (101), and (111)) of grains for extracting the dynamic mechanical responses of AlON single crystals. Our results reveal dynamic plasticity of AlON single crystal is governed by a combination of mechanisms, including dislocation motion and amorphization. Significantly, the localized amorphization induced by mechanical deformation causes the softening effect (the lower dynamic hardness). The crystallographic orientation affects the dynamic hardness similarly to the static hardness. In particular, the (111) orientation exhibits the highest hardness, while the (010) orientation is the softest among the three principal orientations. This dependency aligns with the expectations derived from applying the Schmid law. Furthermore, both dynamic and static hardnesses show the typical indentation size effects (ISE), which can be well described using the strain gradient theory associated with the geometrically necessary dislocations. In addition, the size and rate dependencies of dynamic hardness can be decoupled into two independent terms.