A common name for the Gelug school of Tibetan Buddhism (classical Tibetan Dge-lugs-pa), the more austere reformist sect which developed in the Middle Ages, and to which the Dalai Lama and Panchen Lama belong.

It is opposed to the older Red Hat Buddhism, more correctly known as Nyingma. (Or Red Hat may also include all the other schools, Sakya and Kagyu as well as Nyingma.) The terms Red Hat and Yellow Hat were formerly common in Western descriptions of Tibetan and Mongol Buddhism, but are now deprecated as inaccurate and unspecific.

Thanks to Jinmyo for drawing my attention to my misuse.