The heat capacity of colorless synthetic sapphire (&agr; Al2O3, corundum) has been measured from 2 to 25 K. The data above 14 K can be expressed asCv= 1.755×10−3T3+1.905×10−7T5mJ/K·g‐atom. This equation forCvgives &THgr;0= 1035 K, in good agreement with the values calculated from elastic constant data. An extrapolation of these results to higher temperatures is consistent with other data. Below 14 K an anomalous heat‐capacity contribution appears which is about 1.5% ofCvat its maximum. The magnitude of this anomaly corresponds to that which would be given by a few ppm of gaseous or transition‐metal impurities.