Songtsen Gampo (Tibetan: སྲོང་བཙན་སྒམ་པོ, Wylie: srong btsan sgam po) was the 33rd King (Tsenpo) of Tibet from 618 or 629 until his death in 650, and the founder of the Tibetan Empire. The first of the "Three Dharma Kings of Tibet", he formally introduced Buddhism to Tibet and built the Jokhang with the influence of his queen Bhrikuti, from the Licchavi kingdom of Nepal. He unified the Tibetan Plateau, conquered lands adjacent to Tibet, and moved the capital to the Potala Palace in Lhasa. His minister Thonmi Sambhota created the Tibetan script and Classical Tibetan, the first literary and spoken language of Tibet.

His queen mother is identified as Driza Thökar (Tibetan: འབྲི་བཟའ་ཐོད་དཀར་, Wylie: 'bri bza' thod dkar). The exact date of his birth and his enthronement are not certain, and in Tibetan history it is generally accepted that he was born in an Ox year of the Tibetan calendar. According to Tsepon W. D. Shakabpa, he ascended the throne at age thirteen, in 614, and reigned at least until 648.

As Tibetan kings usually ascended to the throne around age 13, several earlier dates are also suggested for the birth of Songtsen Gampo include 569, 593 or 605.

It is said that Songtsen Gampo was born at Gyama in Meldro, a region to the northeast of modern Lhasa, the son of the Yarlung king Namri Songtsen. The book The Holder of the White Lotus says that it is believed that he was a manifestation of Avalokiteśvara, of whom the Dalai Lamas are similarly believed to be a manifestation. His identification as a cakravartin and incarnation of Avalokiteśvara began in earnest in the indigenous Buddhist literary histories of the 11th century.

Songtsen Gampo's mother, the queen, was a member of the prominent Tsépong clan (Wylie: tshe spong, Tibetan Annals Wylie: tshes pong), which played an important part in the unification of Tibet. Her name is recorded variously but is identified as Driza Tökar ("the Bri Wife named White Skull Woman", Wylie: 'bri bza' thod dkar, Tibetan Annals Wylie: bring ma tog dgos).

Songtsen Gampo had six consort queens, of whom four were Tibetan and two were foreign born. The highest-ranking consort was Pogong Mongza Tricham (Wylie: pho gong mong bza' khri lcam, also called Mongza, "the Mong clan wife", who is said to have been the mother of Gungsong Gungtsen. Other notable wives include a noble woman of the Western Xia known as Minyakza ("Western Xia wife", Wylie: mi nyag bza'), and a noble woman from Zhangzhung. Well-known even today are his two foreign wives: the Nepali princess Bhrikuti ("the great lady, the Nepalese wife", Wylie: bal mo bza' khri btsun ma) as well as the Chinese Princess Wencheng ("Chinese Wife", Wylie: rgya mo bza'). Songtsen sponsored the building of two temples to house the images of Buddha brought by his Nepalese and Chinese wives, however he showed little interest in propagating Buddhism otherwise, and was buried according to pre-Buddhist protocols and rituals when he died.

Songtsen Gampo's heir, Gungsong Gungtsen, died before his father, so his younger son Mangsong Mangtsen inherited the throne. Two Dunhuang sources give different mothers for Mangsong Mangtsen: the Tibetan Annals say the mother was the Tsenmo (Princess Wencheng) of Songtsen while the Genealogy says it was Mangmoje Trikar Wylie: mang mo rje khri skar). It is unlikely that the mother was the Tsenmo because the Annals did not use the honorific kinship term yum (mother) for her.

Tibetan Empire-era documents found at Dunhuang say that Songtsen Gampo also had a sister Sad-mar-kar (or Sadmarkar) and a younger brother bTzan-srong who was betrayed and died in a fire, c. 641. According to one partially damaged scroll from Dunhuang, there was hostility between Sadmarkar and bTzan-srong, who was then forced to settle in gNyal (southeast of the Yarlung River and across the 5,090 metres (16,700 ft) Yartö Tra Pass, which borders on modern Bhutan, and Arunachal Pradesh in India).