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The temperature dependence of the cation distribution in synthetic spinel (MgAl₂O₄) was determined using in-situ time-of-flight neutron powder diffraction. Neutron diffraction patterns of stoichiometric MgAl₂O₄ and slightly non-stoichiometric Mg_0.99Al₂O₄ samples were collected under vacuum on heating from room temperature to 1600 °C, and the cation distribution was determined directly from site occupancies obtained by Rietveld refinement. The equilibrium non-convergent ordering has been analyzed using both the O’Neill-Navrotsky and Landau thermodynamic models, both of which fit the observed behavior well over the temperature range of the measurements. Fitting the data between 560 °C and 1600 °C using the O′Neill and Navrotsky (1983) thermodynamic model yields α = 32.8 ± 0.9 kJ/mol and β = 4.7 ± 2.0 kJ/mol. The fit to the Landau expression for ordering gives values of T_c = 445 ± 109 K and c …