K’ai-yüan-ssu ［開元寺］ (PY Kaiyuansi;  Kaigen-ji): The name given to a number of Buddhist temples, one in each prefecture of China by order of the emperor Hsüan-tsung of the T’ang dynasty. The name K’ai-yüan derives from the date of this imperial edict, which was issued in the twenty-sixth year of the K’ai-yüan era (738). Some of these temples were newly built, and others were existing temples that were renamed K’ai-yüan-ssu. These official temples, along with Buddhism in general, were placed under state control, and they were used also for imperial birthday ceremonies and other national rites and celebrations.