In this study, a dense Al2O3-Y3Al5O12 (YAG) ceramic was synthesized by flash sintering a powder mixture of Al2O3 and Y2O3 in less than 150 seconds at a furnace temperature of 1350 degrees C. The resultant ceramic has a well-defined eutectic structure consisting of alternating Al2O3 and YAG layers. The hardness and fracture toughness of the ceramic were measured to be 18.5 GPa and 4.3 MPa.m(1/2), respectively. These values are comparable to those of similar eutectic ceramics made by directional solidification techniques. The results suggest a new method for making high-performance eutectic ceramics, which could be applied in other systems.