Namkhai Nyingpo (8th/9th century CE) (Wylie: gNubs Nam-mkhaˇi sNying-po) is counted amongst the principal 'twenty-five disciples' of Padmasambhava. Namkhai Nyingpo was a realized practitioner of Shantarakshitaˇs tradition of Sutrayana and 'gradual' Mahayana, as well as simultaneously being one of the most accomplished Tibetan practitioners of the Chinese Chˇan School (East Mountain Teachings), which transmits the T?nmun or 'sudden' tradition of the Mahayana. In addition, Namkhai Nyingpo was also a realized master of the Dzogchen path (Atiyogayana) of 'self-liberation' (Wylie: rang grol), as well as a Master of the Tantric Path (Tantrayana) of transformation (specifically, the three Outer Tantra yana and the Inner Tantra yana bar Dzogchen according to the scheme of the Nyingmapa). 'Namkhai Nyingpo' (Tibetan; Sanskrit: Akasagarbha) may be rendered in English from the Tibetan as 'essence of space' or 'matrix of the sky'.