Hugoniot measurements have been performed on high-purity cubic boron nitride polycrystals in the pressure range up to 296GPa using a two-stage light-gas gun. Hugoniot parameters have been measured by a line reflection method and Fabry–Pérot velocimetry. The Hugoniot elastic limit (HEL) is determined to be 44.3GPa, which is the second highest value after that of diamond. Above the HEL, the Hugoniot compression curve shows a considerable offset from its hydrodynamic compression curve, which is calculated from static-compression data. This result shows that cubic boron nitride preserves its shear strength in the plastic region. Hugoniot data indicate that the cubic phase of boron nitride is stable in the pressure range up to 296GPa.