Sonam Tsemo (tib.: bsod nams rtse mo; 1142–1182), an important Tibetan sprititual leader and Buddhist scholar, was the second of the so-called Five Venerable Supreme Sakya Masters of Tibet, the founding fathers of the Sakya-tradition.
He was born in the year of the water dog of the second cycle at Sakya and was acclaimed as an incarnation of Durjayachandra. He received extensive spiritual training from his father, Sachen Kunga Nyingpo, the first of the five founding fathers of the Sakya-tradition. At age 17, he went to Sangphu Neuthok and deepened his studies under the famous scholar Chapa Chokyi Senge. His studies included Paramita, Madhyamaka, Pramana, Vinaya and Abhidharma. By the time he was eighteen he had mastered the triple discipline of teaching, debate and composition. After his return to Sakya, he held the throne of the monastery for three years and then passed the authority to his younger brother, Jetsun Dragpa Gyaltsen, the third of the five founding fathers. He dedicated the rest of his life to studies and meditation and died in 1182, the water tiger year, at age 41. He is said to have attained the second bhumi.