Phayre's Leaf Monkey (Trachypithecus phayrei), also known as Phayre's Langur, is a species of lutung found in Southeast Asia. It is classified as endangered on the IUCN Red List and listed on Appendix II of CITES.

Its range includes Bangladesh, India, Myanmar, China, Thailand, Laos and Vietnam. In Thailand it's distribution is limited to parts of the North and North East of the country as well as the Western Forest Complex. So a chance to see one of these rare animals could not be missed and a trip was arranged to Phu Khieo in the north of Chaiyaphum to see if I could see one and photograph one in the wild.

In Thai it is known as the Kang Waen, which shows one of the issues with the use of common names against scientific names as it loosely translates to "spectacled monkey" which is an alternate common name for another species of langur, the Dusky Langur (Trachypithecus obscurus). It is mostly arboreal and feeds on leaves of a large number of tree species.It is mostly arboreal and feeds on leaves of a large number of tree species.

Phu Khieo Wildlife Sanctuary is part of the Western Isaan Forest Complex, a ca. 6000 sqkm network of eight connected Wildlife Sanctuaries and National Parks. The forest harbors an intact and diverse community of predators (including clouded leopards, leopards, and tigers) and large populations of ungulates.

The species epithet commemorates Arthur Purves Phayre. Whether this was because he was a "naturalist" I know not but I suspect it was to honour him somewhat as he was senior British Colonialist and the Commissioner of British Burma in the late 1800s.