Metal-matrix composites (MMC) have great potential to be used in high-performance aerospace and automobile applications. It is important, therefore, to develop secondary processing for MMCs which can effectively produce complex engineering components directly from wrought products. Many studies now have been performed that demonstrate superplasticity can be developed in MMCs. Superplasticity has been reported in some Mg alloys, including ZK60, AZ31, AZ61, and Mg-Li alloys. But, none of these alloys showed superplasticity at high strain rates. Although HSRS has been extensively demonstrated in Al-base MMCs, both in PM and IM products, neither conventional superplasticity nor HSRS has yet been shown in any Mg-base composite. The purpose of this paper is to present, for the first time, the observation of HSRS in a 17 vol% SiC particulate-reinforced ZK60A magnesium composite (ZK60/SiC/17p).