Baltistan (), also known as بلتیول (Baltiyul) in the Balti language, is a region in northern Pakistan. It borders Xinjiang Autonomous Region of China. It lies in the Karakoram mountains just to the south of K2, the world's second highest mountain. It is an extremely mountainous region, with an average altitude of over 3,350 m (11,000 ft). It is inhabited principally by Balti Shi'a Muslims of Tibetan descent who converted from Tibetan Buddhism before the 16th century.