Khao Phra Wihan National Park (Thai: อุทยานแห่งชาติเขาพระวิหาร) is a protected natural area in Sisaket Province, Thailand, that contains numerous ruins of the 11th century Khmer Empire. The park lies 98 km (61 mi) south of the town of Sisaket, at the end of Thai highway 221. Sited on a red stone cliff that is part of the Dangrek mountain range on the southern edge of the Khorat Plateau, it abuts the international border between Thailand's Sisaket Province and Cambodia's Preah Vihear Province. The name of the cliff in the Royal Thai General System of Transcription is Pha Mo I Daeng (ผามออีแดง).