The single-crystal elastic moduli of yttria have been measured by Brillouin spectroscopy up to 1200 °C. The room temperature values obtained are C11=223.7±0.6 GPa, C44=74.6±0.7 GPa, and C12=112.4±1.1 GPa. The resulting bulk and (Voigt–Reuss–Hill) shear moduli are K=149.5±1.0 GPa and GVRH=66.3±0.8 GPa, respectively. These agree much more closely with experimental values reported for polycrystalline samples than do previous single-crystal measurements. Linear least squares regressions to the variation of bulk and shear moduli with temperature result in derivatives of dK/dT=-17±2 MPa/°C and dGVRH/dT=-8±2 MPa/°C. Elastic anisotropy was found to remain essentially constant over the temperature range studied. © 2001 American Institute of Physics.