Abstract: A transparent yttriastabilized zirconia (YSZ) single crystal becomes purple after 200keV Xe+irradiation. Calculation of TRIM 96 shows that 200keV Xe+ ions cause peak displacement levels of ~350dpa (displacement per atom) at the depth of 30nm in a YSZ single crystal at a dose of 1×1017cm-2, and crosssectional TEM images and diffraction pattern show that there is no amorphization. Optical absorption measurements show that a broad absorption band appears at a dose of 1×1016cm-2. For the 1×1016cm-2 and 1×1017cm-2 Xe+irradiated crystals, the absorption bands are centered at 522nm and 497nm, respectively. The bands are assigned to electrons trapped at oxygen vacancies nearest to Zr cations (Ftype centers) and to oxygen ions with trap holes adjacent to yttria cations (Vtype center