Trisong Detsän or Trisong Detsen (Tibetan: ཁྲི་སྲོང་ལྡེ་བཙན, Wylie: khri srong lde btsan, Lhasa dialect IPA: ʈʂʰisoŋ tetsɛ̃) was the son of Me Agtsom and one of the emperors of Tibet. He ruled from 755 until 797 or 804 CE. Trisong Detsen was the second of the Three Dharma Kings of Tibet, playing a pivotal role in the introduction of Buddhism to Tibet and the establishment of the Nyingma or "Ancient" school of Tibetan Buddhism.

The empire Trisong Detsen inherited had declined somewhat from its greatest extent under the first Dharma King, Songtsän Gampo. Disintegration continued during Trisong Detsen's reign when, in 694, Tibet lost control of several cities in Turkestan and, in 703, Nepal broke into rebellion. Meanwhile, Arab forces vied for influence along the western border lands of the Tibetan empire.

Trisong Detsen is very important to the history of Tibetan Buddhism as one of the three 'Dharma Kings' (Tibetan:chosgyal) who established Buddhism in Tibet. The Three Dharma Kings were Songtsän Gampo, Trisong Detsen, and Ralpacan.

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