The scientific name Presbytis phayrei was used by Edward Blyth in 1847 for two young individuals captured alive in the Arakan Mountains in Myanmar.

[3] Phayre's langur is one of the most widespread members of the genus, but its actual distribution and intraspecific taxonomy remain controversial.

Currently, the name Phayre's leaf monkey refers to T. phayrei, residing in forests of East Bengal, Northeast India and western Myanmar, specifically, areas to the west of the Chindwin and Irrawaddy Rivers.

[8] Like most Old World monkeys, it has the dental formula of 2.1.2.32.1.2.3[9] Distinctive to other colobines Phayre's langur show craniodental adaptations such as medially positioned rows of teeth and stronger masseter pterygoid muscles for seed-eating.

[10] Pharye's langur is found in tropical, deciduous, and evergreen forests of North-East India, Eastern Bangladesh, and Western Myanmar.

[11] In India, the most common roosting trees range from heights of 6–15 m (20–49 ft) and have an extensive canopy, e.g., Ficus hispida and Triadica sebifera in Mizoram.

Based on observations in the wild, a loud “kah-kah-kah” is used to sound alarm in the troop, while in the presence of a predator a softer “whoo” call is used.

[11] It is seen that males and juveniles tend to spend more time moving than adult females, who also have the highest percentage of resting among them.

In Dampa Tiger Reserve, the Phayre's langurs feeds on Citrus grandis, Gmelina arborea, Ficus maclellendii, Buetneria pilosa, with a preference towards bamboos such as Musa ornata, Melocanna baccifera and Dendrocalamus longispathus during summer.

[7] In Satchari National Park in Bangladesh, they feed primarily on Ficus hispida, Albizia chinensis, and Vachellia nilotica.

[11] The high bamboo consumption in their diets is attributed to the abundance of this plant in North-East India because of its invasive nature.

[20] Phayre's langurs living in local rubber plantations in Mizoram majorly consume leaves of Hevea brasiliensis showing that diet is affected by the plant diversity in its home range.

The major threats to Phayre's langur are habitat destruction, fragmentation, logging, roadkill, ecotourism, electrocution and hunting.

[15] In both India and Bangladesh, Pharye's langur is protected through national and local legislation and through implementation of international conservation laws and policies, i.e., the Wild Life (Protection) Act, 1972, in India and Wildlife (Conservation and Security) Act, 2012, in Bangladesh .