[en] This paper reports on the radiation damage of gamma aluminum oxynitride (γ-AlON) transparent ceramic, which remarkably degrades UV–vis transparency and hence limits its applications in optoelectronic devices. The radiation-induced optical absorption of the as-sintered γ-AlON consists of at least two subbands: one is in the UV region with a peak at 270 nm and the other optical absorption band centers at 550 nm, covering the whole visible light spectrum, which makes the sample colored. Interestingly, all the radiation-induced color centers can be completely ‘bleached’ by low temperature annealing. In the thermoluminescence curve, we observed a broad luminescence in the range of 25–300 °C with the peak at 120 °C. Furthermore, the x-ray excited luminescence spectra revealed that there exist multiple emission centers in the γ-AlON. Based on this experimental fact, the radiation damage and luminescent mechanisms were studied. These optical properties of the γ-AlON are considered to be related to defect states. In the as-sintered γ-AlON, charge balancing is realized by the co-existence of ${\text{V}}_{\text{Al}}^{\mathrm{\prime <!--\; ???\; -->}\mathrm{\prime <!--\; ???\; -->}\mathrm{\prime <!--\; ???\; -->}}$ and ${\text{O}}_{\text{N}}^{\bullet <!--\; ???\; -->}$, and the predominant defect form is $[{\text{V}}_{\text{Al}}^{\mathrm{\prime <!--\; ???\; -->}\mathrm{\prime <!--\; ???\; -->}\mathrm{\prime <!--\; ???\; -->}}-<!--\; ???\; -->{\text{3O}}_{\text{N}}^{\bullet <!--\; ???\; -->}]$, which is optically inactive and no optical absorption occurs. However, isolated ${\text{V}}_{\text{Al}}^{\mathrm{\prime <!--\; ???\; -->}\mathrm{\prime <!--\; ???\; -->}\mathrm{\prime <!--\; ???\; -->}}$ and ${\text{O}}_{\text{N}}^{\bullet <!--\; ???\; -->}$ can be formed by irradiation and it is these that are responsible for the radiation damage of γ-AlON transparent ceramic. In the end, the UV absorption and visible-light absorption in the irradiated sample were ascribed to V_Al-related and O_N-related intrinsic defects, respectively. (paper)