Raman spectra of Y2O3 single crystal were recorded at room temperature in a diamond anvil cell up to a pressure of 22 GPa. Two phase transitions were detected at pressures of 12 and 19 GPa. The different phases were identified with the three structures exhibited by rare-earth (RE) sesquioxides: cubic (C-type), monoclinic (B-type), and rhombohedral (A-type) phases. The first transition corresponds to the C-->B transformation and the second transition to the B-->A transformation. The reversibility of the two phase transitions as well as the evolution of the Y-O bonds under high pressure is discussed. (C) 2000 Elsevier Science Ltd.