We investigated high-pressure induced phase transitions in Y2O3 and Eu-doped Y2O3 (Y2O:Eu3+) using angular dispersive synchrotron x-ray diffraction, Raman spectroscopy, and photoluminescence (PL). With increasing pressure, we observed a series of phase transformations in Y2O3:Eu3+, which followed a structure sequence of cubic→monoclinic→hexagonal, while Y2O3 followed a sequence of cubic→hexagonal. During decompression, both hexagonal structured Y2O3 and Y2O3:Eu3+ transformed into monoclinic phases which were quenchable back to ambient pressure. Raman and PL measurements shed additional light on the different phase transition behavior in these two samples.