The elastic properties of a synthetic single‐crystal spinel with a composition of MgO·2.6Al2O3have been determined at 25°C and up to 2 kbar by measuring propagational velocities of ultrasonic waves using the method of pulse superposition. The isotropic moduli and Poisson's ratio were computed from the single‐crystal values using the Voigt‐Reuss‐Hill approximation.Values of the adiabatic elastic moduli at 1 bar and 2 kbar and at 25°C arec11c12c441bar2985.71537.21575.8(kbar)2kbar2995.51545.01577.5(kbar).The adiabatic bulk modulus was computed to be 2019.9 kbar, and the pressure derivative of the adiabatic bulk modulus was found to be 4.18.