The reaction kinetics of gypsum dissolution are important for establishing an optimum gypsum content in portland cement. In this paper, the temperature dependence of dissolution rates was measured by tracking changes in solution composition and surface area with time. The rate coefficient increases with temperature and the specific surface area decreases with ongoing dissolution. The dissolution rate depends on the solution's saturation index to an exponent of approximately 1.5. The apparent activation enthalpy is approximately 34 kJ mol−1, independent of saturation index and surface area, suggesting that dissolution is controlled by surface reaction rather than mass transport. The activation enthalpy is interpreted as the energy required to cooperatively break all the ionic bonds at occupied kink sites of the gypsum-water interface. Activation enthalpies similar in magnitude have been reported for other calcium salts, which may indicate that all of these processes involve breaking ionic calcium-oxygen bonds of similar strengths.