The Kagyu, Kagyupa, or Kagyud (Tibetan: བཀའ་བརྒྱུད་པ, Wylie: bka' brgyud pa) school, also known as the "Oral Lineage" or Whispered Transmission school, is today regarded as one of six main schools (chos lugs) of Himalayan or Tibetan Buddhism, the other five being the Nyingma, Sakya, Jonang, Bon and Gelug. Along with the later two the Kagyu is classified as one of the Sarma or "New Transmission" schools since it primarily follows the Vajrayāna or Tantric teachings based on the so-called New Tantras, i.e., those translated during the second diffusion of the Buddha Dharma in Tibet. Along with the Nyingma and Sakya schools it is a Red Hat sect.

Like all schools of Tibetan Buddhism, the Kagyu consider their practices and teachings inclusive of the full range of Buddha's teachings (or three yāna), since they follow the fundamental teachings and vows of individual liberation and monastic discipline (Pratimoksha). Those teachings in turn accord with the Mulasarvastivada tradition of the Śrāvakayāna (sometimes called Nikāya Buddhism or "Hīnayāna" ); the Bodhisattva teachings, vows of universal liberation and philosophy of the Mahāyāna; and the profound means and samaya pledges of the Secret Mantra Vajrayāna.

What differentiates the Kagyu from the other schools of Himalayan Buddhism are primarily the particular esoteric instructions and tantras they emphasize and the lineages of transmission they follow.

Due to the Kagyu tradition's particularly strong emphasis on guru devotion and guru yoga, and the personal transmission of esoteric instructions (dam ngag or man ngag) from master to disciple, the early Kagyu tradition soon gave rise to a bewildering number of independent sub-schools or sub-sects centered round individual charismatic Kagyu teachers and the hereditary lineages as well as mindstream emanation lineages.

Read more about Kagyu:  Nomenclature, Orthography and Etymology, Shangpa Kagyu, Marpa Kagyu and Dagpo Kagyu, Kagyu Literature