Which Indian master is considered a second Buddha in Tibetan Buddhism?

The Indian master considered a second Buddha in Tibetan Buddhism is Padmasambhava.

Padmasambhava, also known as Guru Rinpoche, is an eighth-century Indian tantric master credited in Tibetan Buddhist tradition with helping establish Vajrayana in Tibet. Tibetan accounts say that King Trisong Detsen invited him to Tibet, where he helped tame hostile local spirits, advance Buddhist tantric practice, and establish Samye, traditionally regarded as Tibet’s first Buddhist monastery.

His influence is especially strong in the Nyingma, or “Ancient,” school, which regards him as a founding figure. Padmasambhava is associated with both transmitted teachings and terma, hidden treasure texts believed to be discovered by destined treasure revealers when the time is right. His principal Tibetan students traditionally include Yeshe Tsogyal, a revered female master, as well as the king and other important practitioners.

The title “second Buddha” reflects religious veneration rather than a universally agreed historical label. Padmasambhava is traditionally viewed as an emanation of, or foretold by, Shakyamuni Buddha. His biographies combine historical memories of an Indian tantric teacher with miracle stories and later hagiography, which expanded considerably from the twelfth century onward.