Katok Monastery (Wyl. kaḥ thog) aka Katok Dorje Den — one of the Six "Mother" Nyingma Monasteries. It was founded by Katok Dampa Deshek, younger brother of Phagmodrupa Dorje Gyalpo, in 1159. After the original monastery had fallen into disrepair, a new monastery was built on the site in 1656 by Tertön Düddul Dorje (1615-72) and Rigdzin Longsal Nyingpo (1625-92). There were approximately 800 monks at the monastery before the Chinese invasion of Tibet.
The monastery had a reputation for fine scholarship and produced some of the greatest scholars in Tibetan history, such as Katok Rigdzin Tsewang Norbu (1698-1755) and Getse Pandita Gyurme Tsewang Chokdrup (b. 1761). More recently, Katok Situ Chökyi Gyatso and Khenpo Ngawang Palzang, aka Khenpo Ngakchung, were among the greatest lamas associated with the monastery.