A fluorite-related phase of Gd2O3, with a tetragonal unit cell of a=5.65 Å and c=5.37 Å, was attained in this study. The new phase was found either in a thin Gd2O3 film (∼18 Å), which was epitaxially grown on GaAs(100), or in a disordered (by mild Ne+-ion sputtering) and recrystallized (by UHV annealing) thin cubic α-Gd2O3 film. The structural characteristics of the new oxide films were studied using in situ reflection high-energy electron diffraction, secondary-electron imaging, and single-crystal x-ray diffraction.