Highly transparent Y2O3 ceramics using TiO2 as an additive were synthesized by presintering and hot isostatic pressing (HIP). The effects of TiO2 contents and sintering conditions on the optical properties of the final transparent ceramics were investigated. A small amount (0.04-0.16 wt%) may decrease the densification temperature by about 200 degrees C. The Y2O3 ceramics doped with 0.16 wt% TiO2 revealed a transparency of 82% in the wavelength range 1-6 m. The thermal conductivity of the samples is about 11.8 W/m K at 25 degrees C, which is close to that of the undoped Y2O3 ceramics.