(Lochen) Rinchen Zangpo (958–1055), also known as Mahaguru, was a principal lotsawa or translator of Sanskrit Buddhist texts into Tibetan during the second diffusion of Buddhism in Tibet (or the New Translation School or New Mantra School period). He was a student of the famous Indian master, Atisha. His associates included (Locheng) Legpai Sherab. Zangpo's disciple Guge Kyithangpa Yeshepal wrote Zangpo's biography. He is said to have built over one hundred monasteries in Western Tibet, including the famous Tabo Monastery in Spiti, Himachal Pradesh, and Poo in Kinnaur.
Rinchen Zangpo had been sent as a young man by King Yesh-es-od, who seems to have been ruler of Zanskar, Guge, Spiti and Kinnaur, with other young scholars to Kashmir and other Buddhist centres to study and bring back Buddhist teachings to Western Tibet. He was possibly the single most important person for the 'Second Propagation of Buddhism' in Tibet. Some sources claim he became king of the western Himalayan Kingdom of Guge.
Among his translations are the Viśeṣastavaṭikā by Prajñāvarman, which he undertook together with Janārdhana. 
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