Enthalpies of formations of Sr 4 Ga 2 O 7 , SrGa 2 O 4 , and SrGa 12 O 19 are measured for the first time using high-temperature oxide-melt drop-solution calorimetry. A self-consistent thermodynamic dataset for the SrO – Ga 2 O 3 system is derived by means of the CALPHAD method based on these data, literature phase diagram information, and recent structural studies. In total seven compounds, Sr 4 Ga 2 O 7 , Sr 10 Ga 6 O 19 , Sr 3 Ga 2 O 6 , Sr 3 Ga 4 O 9 , SrGa 2 O 4 , SrGa 4 O 7 , and SrGa 12 O 19 are included. Their enthalpy of formation as well as the enthalpy of mixing of the liquid is strongly exothermic. The systematic variation of thermodynamic properties with composition is discussed in terms of the structural relationships between strontium gallates and the possible formation of associates in the liquid phase.