In the present work, we report the processing of ultrahard tungsten carbide (WC) nanocomposites with 6 wt% zirconia additions. The densification is conducted by the spark plasma sintering (SPS) technique in a vacuum. Fully dense materials are obtained after SPS at 1300degreesC for 5 min. The sinterability and mechanical properties of the WC-6 wt% ZrO2 materials are compared with the conventional WC-6 wt% Co materials. Because of the high heating rate, lower sintering temperature, and short holding time involved in SPS, extremely fine zirconia particles (similar to100 nm) and submicrometer WC grains are retained in the WC-ZrO2 nanostructured composites. Independent of the processing route (SPS or pressureless sintering in a vacuum), superior hardness (21-24 GPa) is obtained with the newly developed WC-ZrO2 materials compared with that of the WC-Co materials (15-17 GPa). This extremely high hardness of the novel WC-ZrO2 composites is expected to lead to significantly higher abrasive-wear resistance.