Sinharaja Forest Reserve is considered one of the most important natural habitats in Sri Lanka; this virgin rain forest is located in the south western lowland wet zone eco-region of the country. The vegetation is tropical wet evergreen forest and the area covered by the rain forest is more than 11000 hectares. Sinharaja has an incredibly high rate of bio-diversity; it was identified as an International Man and Biosphere Reserve in 1978 and was declared a UNESCO World Heritage Site in 1989.

The forest is home to a huge diversity of species both flora and fauna with a large proportion of those being indigenous to the country and some more specifically endemic to Sinharaja itself. Out of the 331 woody trees and lianas identified here 192 (60%) are endemic at Sinharaja. This is the only relatively undisturbed rain forest of any considerable size in Sri Lanka and many of the plants are very rare and are represented by only one individual of its kind in a large area.

Sinharaja is a paradise for birdwatchers; 141 species of birds have been recorded in Sinharaja and 28 out of the 34 endemic birds in Sri Lanka are also found in this majestic rain forest. Many indigenous birds such as Layard's parakeet (Psittacula calthripae), the Jungle fowl (Gallus lafayetii ), the Spur fowl (Galloperdix bicalcarata), the Ceylon Wood Pigeon (Columba torringtonii), the Ceylon Hanging Parrot (Loriculus beryllinus), the Ceylon Grey Hornbill (Ocyceros gingalensis), the Ashy-headed Laughing Thrush (Garrulax cinereifrons), the Brown- capped Babbler (Pellorneum fuscocapillum), the Red-faced Malkoha (Phaenicophaeus pyrrhocephalus) and the Ceylon Blue Magpie (Urocissa ornate) among others, are prominent in this area. There are 65 species of butterflies found in Sinharaja, out of which one species is endemic.

Because of the dense vegetation, wildlife is not as easily seen as at dry-zone national parks such as Yala or Udawalawa. However, it is believed that several leopards and elephants are living in Sinharaja but sightings have not been recorded in the recent past. 40 mammals have been identified in this reserve, out of which 7 are endemic. Purple-face langur is the most commonly seen mammal, which is also an endemic species. 29 species of snakes & reptiles are found in Sinharaja with 14 species being endemic; also 19 species of amphibians have also been recorded with 08 species being endemic.

The rain forest is naturally decorated by beautiful waterfalls and picturesque lakes flowing throughout the year due to the high rainfall in the area. 10 species of fish have also been recorded in Sinharaja out of which 7 species are endemic.

From Colombo, Sinharaja could be reached either on the Matugama route via Kalutara or Kalawana route via Ratnapura. From the South coast you can enter the reserve from the Pitadeniya Camp via Galle and Deniyaya.

For visitors who wish to spend a few days exploring the rain forest, there are few accommodation options available. Mainly the accommodation inside and bordering the reserve is very basic but there are also a few good hotels in very close proximity.