Kanneliya-Dediyagala-Nakiyadeniya, or KDN, is a forest reserve in the Southern Province of Sri Lanka. Identified as one of the most floristically rich areas in South Asia; this forest region is the last remaining large rainforest in Sri Lanka, other than the Sinharaja Rainforest. The forest is situated 35km northwest of the City of Galle; and is a major catchment area for two of the most important rivers in southern Sri Lanka, Gin Ganga and Nilwala Ganga. Designated as a biosphere reserve in 2004 by UNESCO, the Kanneliya forest reserve home to many endemic plant and animal species.

The Kanneliya Forest reserve has large number of endemic flora and fauna; with 17 percent of lowland endemic floral species confined to this forest area, and 41 species of endemic fauna living there. The vegetation is representative of the Sri Lankan lowland rainforests. The forest also harbours numerous medicinal plants and rare plants within the forest.27 percent of the floral species within the forest are listed as vulnerable, and 45 percent are in the rare plants category. Kanneliya also has a total of over species of fauna; including species of mammals, species of snakes, and several species of avian life and fish. Amongst the bird species here;  birds are endemic with of them only seen within the KDN forest complex. Some of these are the Sri Lankan spur fowl, Sri Lankan jungle fowl, Sri Lankan grey hornbill, red-faced Malkoha, orange-billed babbler and the Sri Lankan blue magpie. Twenty percent of Sri Lanka’s endemic freshwater fishes inhabit in the waters of Gin River and Nilwala River.