The equilibrium phase diagram was determined for the Eu2O3−In2O3 system. An induction furnace, having an iridium crucible as the heating element (susceptor), was used to establish the solidus and liquidus curves. The 1:1 composition melts congruently at 1745 ± 10 °C. Melting point relations suggest that the 1:1 composition is a compound with solid solution extending both to 31 mole percent In2O3 and 71 mole percent In2O3. The compound is pseudohexagonal with aH = 3.69 A and cH = 12.38 A. Isostructural phases also occur in the 1:1 mixtures of both Gd2O3 and Dy2O3 with In2O3. The melting points of Eu2O3 and In2O3 were determined to be 2,240 ± 10 °C and 1910 ± 10 °C respectively. A eutectic occurs in the Eu2O3−In2O3 system at 1,730 °C and about 73 mole percent In2O3. The indicated uncertainties in the melting points are conservative estimates of the overall inaccuracies of temperature measurement.