Dhansiri Reserve Forest is a reserve forest in Karbi Anglong district of Assam. This reserve forest is rich in elephants. This reserve forest borders Intanki National Park of Nagaland which is rich in both birds and mammals.

It also borders the adjacent forests of Daldali Reserve forest; Barlangpher District Reserve Forest and Tamulbari. This reserve forest (RF) is a part of Dhansiri-Lungding Elephant Reserve. This was notified by Government of India in the year 2003. The area of Dhansiri Reserve Forest consists of surging plains to low hills, which are part of Karbi plateau.

Dhansiri Reserve Forest faces a number of landslides and soil erosion. It is because the rivers like Dhansiri River, Jamuna river, Lungding river, Borlangpher river, Diphu Nala river and others continuously erode the soils of the reserve forest. The area of Dhansiri Reserve Forest has become much lower in height than the northern plateau and southern hills. Geographically, the area is known as the Dhansiri Gap. The lowest parts of the Dhansiri Reserve Forest is about 150 m above msl. The highest point is 598 m (Thangnangsip) in Khelma area. The elevation of the larger part of Dhansiri Reserve Forest is 200-250 meters.

Dhansiri River is the major river in the region of Dhansiri Reserve Forest. This river marks the southern and south-eastern boundary of the elephant reserve. Other important rivers include the Lungding River, Barlangpher River, Chhotalangpher River, and Diphu Nala River. Most of the smaller "nullahs" or small rivulets become dry in winter and summer times. The climate of Dhansiri Reserve Forest is `tropical monsoon type.` The summers are hot and wet, while the winters are cool and dry. The area is in the low rainfall zone (a rain-shadow zone, where the orographic rainfall happens) of north-eastern India.

The forest type of Dhansiri Reserve Forest is Tropical Moist Deciduous and Tropical Semi evergreen. The top canopy consists of Tetrameles nudiflora, Amoora wallichii, Artocarpus chaplasha, Michelia champaca, Mesua ferrea, Phoebe goalparensis, Gmelina arborea, Duabanga sonneratioides, Dillenia scabrella, Canarium resiniferum and Mansonia dipikae (endemic to the area). The middle layer consists of Eugenis jambolana, Premna benghalensis, Dillenia indica, D. scabrella, Albizzia procera and Emblica officinalis. The under storey of Dhansiri Reserve Forest has Zizyphus spp., Clerodendron spp., Calamus spp., with Lantana camara in the open patches. The abandoned jhum cultivation is covered with various grasses such as Themeda villosa, Saccharum procerum, Imperata cylindrica, and shrubs Eupatorium odoratum. In the depression zone of Dhansiri Reserve Forest are Alpinia allughas, Arundo donax and Neyraudia reynaudiana grasses (both locally called "Nal") occur. The plantations of the Forest Department in Dhansiri Reserve Forest are mainly Tectona grandis (Indian Teak), Gmelina arborea and Albizzia procera.