Tri Songdetsen (Tibetan: ཁྲོ་སྲོང་ལྡེ་བརྩན། ཁྲི་སྲོང་ལྡེ་བཙན, Wylie: khri srong lde brtsan/btsan, ZYPY: Chisong Dêzän, Lhasa dialect: [ʈʂʰisoŋ tetsɛ̃]) was the son of Me Agtsom, the 38th emperor of Tibet.

The Skar-cung pillar erected by Sadnalegs (ruled c. 800-815) says that during the reign of Tri Songdetsen, "shrines of the Three Jewels were established by building temples at the centre and on the borders, Bsam-yas in Brag-mar and so on".

[4] In post-imperial sources, is claimed to have invited Padmasambhava, Śāntarakṣita, Vimalamitra, and various other Indian teachers to come to Tibet to spread the latest understanding of the teaching.

[5] Yeshe Tsogyal, previously either the consort or wife of Tri Songdetsen, became a great master after studying with Padmasambhava, and is considered the Mother of Buddhism.

Stein (1972: p. 66-67) holds that Kamalaśīla disseminated a "gradualist approach" to enlightenment, consisting of purificatory sādhanā such as cultivating the pāramitās.

Tri Songdetsen next sought to expand westward, reaching the Amu Darya and threatening the Abbasid Caliph, Harun ar-Rashid.

Tri Songdetsen would be preoccupied with Arab wars in the west while taking pressure off his Chinese opponents to the east and north until his rule ended in 797.

The Testament of Ba, a Tibetan historical text which may date back to the 9th century, claims that Muné Tsenpo insisted that his father's funeral be performed according to Buddhist rather than traditional rites.

[11][12] Whatever the case, both the Old Book of Tang and the Tibetan sources agree that, since Mune Tsenpo had no heirs, power passed to his younger brother, Sadnalegs, who was on the throne by 804 CE.

[13][14] The other brother, Mutik Tsenpo, was apparently not considered for office as he had previously murdered a senior minister and had been banished to Lhodak Kharchu near the Bhutanese border.