The Geluk (dge lugs) School was founded by Tsongkhapa (1357-1419), Tibet's best known religious reformer and arguably its greatest philosopher. The first monastery he established was that of Ganden, and to this day its head, the Ganden Tripa, is nominal head of the school though its most powerful figure is unquestionably the Dalai Lama.

A great admirer of the Kadam teachings, Tsongkhapa was an enthusiastic promoter of the Kadam School's emphasis on the Mahayana principles of universal compassion as a fundamental spiritual orientation. He combined this with a strong emphasis on the cultivation of in-depth insight into the doctrine of emptiness as propounded by the great Indian masters Nagarjuna (2nd century) and Chandrakirti (7th century). Tsongkhapa said that these two aspects of the spiritual path, namely compassion and insight into wisdom, must be rooted in a whole-hearted wish for liberation, all impelled by a genuine sense of renunciation. He called these the "Three Principal Aspects of the Path", and suggested that it is on the basis of these three that one must embark on the profound path of Vajrayana Buddhism. The Geluk sect is the only Tibetan sect that insists on the celibacy of its clergy.

The central teachings of the Geluk School are Lamrim, or the "Stages of the Path", based upon the teachings of the Indian master Atisha (circa 11th century) and the systematic cultivation of the view of emptiness. This is combined with the deity yoga meditations of Highest Yoga Tantra deities such as Guhyasamaja, Chakrasamvara, Yamantaka and Kalachakra, where the key focus is the realization of the indivisible union of bliss and emptiness.

By the end of 15th century, Geluk had become the most dominant School of Tibetan Buddhism, and from the period of "The Great Fifth" in the 17th century the Dalai Lamas have held political power in Tibet.

See also: Zaya Pandita