thumb|right|300px|A statuette of Longchenpa
Longchen Rabjam Drimé Özer (), or simply Longchenpa (1308–1364, "The Vast Expanse") was a Tibetan scholar-yogi of the Nyingma school, the 'Old School' of Tibetan Buddhism. According to tibetologist David Germano, Longchenpa's work led to the dominance of the Longchen Nyingthig lineage of Dzogchen, the Great Perfection, over the other Dzogchen traditions. He is also responsible for the scholastic systematization of Dzogchen thought within the context of the wider Tibetan Vajrayana tradition of Buddhist philosophy.
Dzogchen thought was highly developed among both the Old School and New Sarma schools. Germano also notes that Longchenpa's work is "generally taken to be the definitive expression of the Great Perfection with its precise terminological distinctions, systematic scope, and integration with the normative Buddhist scholasticism that became dominant in Tibet during the thirteenth and fourteenth centuries."
Longchenpa is known for his voluminous writings, including the highly influential Seven Treasuries and his compilation of the Dzogchen text and commentary, the Nyingtig Yabshi, The Inner Essence in Four Parts.' Longchenpa was also a Tertön or treasure revealer, and some of his works, like the Khadro Yangtig, are considered terma and revealed treasure texts. Longchenpa's oeuvre of over 270 texts encapsulates the core of Nyingma thought and praxis and is a critical link between the school's exoteric Sutra and esoteric Tantra teachings.
Longchenpa's work also unified the various Dzogchen traditions of his time into a single system. Longchenpa is known for his skill as a poet and his works are written in a unique literary voice which was widely admired and imitated by later Nyingma figures.
Longchenpa was the Khenpo of Samye Monastery, Tibet's first monastery, and the first Buddhist monastery established in the Himalayas. He spent most of his life travelling or in spiritual retreat.
Biography
Incarnation lineage
The incarnation lineage of Longchenpa is traced to Princess Pema Sal (c.758-766), King Trisong Deutsen's daughter and Padmasambhava's student who died young from a bug bite. Padmasambhava briefly revived her to give her the Khandro Nyingtik empowerment.
She incarnated as Pema Ledrel Sal (1291-1315/1319), the "fifth pure rebirth" of Princess Pema Sal, who became a great Terton as prophesied by Padmasambhava. He revealed the Khandro Nyingtik cycle as a terma treasure at the age of 23 years. He then incarnated as the great Terton and scholar Longchenpa in the 14th century, who then incarnated as the Terton Pema Lingpa (1450-1521).