Highly transparent Y2O3 ceramics were fabricated suppressing the formation of oxygen vacancies during vacuum sintering for the first time. Oxygen stabilization in transparent Y2O3 ceramics was successfully enabled by additional ZrO2 oxygen source considering thermodynamics. The oxygen-stabilized ceramics approached nearly theoretical transmittance without further post-annealing and hot isostatic presssing. This new approach is potentially applicable for the fabrication of other transparent ceramics. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.