Katok Monastery (Tib. ཀཿཐོག་, Wyl. kaHthog) aka Katok Dorje Den (Tib. ཀཿཐོག་རྡོ་རྗེའི་གདན་, Wyl. kaHthog rdo rje'i gdan) — the oldest of the Six "Mother" Nyingma Monasteries. It was founded by Katok Dampa Deshek, younger brother of Phagmodrupa Dorje Gyalpo, in 1159, above Horpo, in East Tibet. The site is considered to be one of twenty-five holy places of Eastern Tibet and represents the main holy place of enlightened activity. After the original monastery had fallen into disrepair, a new monastery was built on the site in 1656 by Tertön Rigdzin Düddul Dorje (1615-1672) and Rigdzin Longsal Nyingpo (1625-1692). 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.
- ཀཿཐོག་པའི་ལོ་རྒྱུས་མདོར་བསྡུས་, kaHthog pa'i lo rgyus mdor bsdus
- Jann M. Ronis, “Celibacy, Revelations, and Reincarnated Lamas: Contestation and Synthesis in the Growth of Monasticism at Katok Monastery from the 17th through 19th Centuries” (unpublished PhD thesis)