Sinharaja Forest Reserve is a lowland rainforest in southwestern Sri Lanka. It is a UNESCO World Heritage Site and a biodiversity hotspot, home to over 60% of the country's endemic plant species and 50% of its endemic animal species.

The forest's high biodiversity is due to a number of factors, including its location, climate, and topography. Sinharaja is situated in the wet zone of Sri Lanka, which receives an average of 2,500 mm of rainfall per year. The forest is also home to a variety of habitats, including river valleys, ridges, and waterfalls. This diversity of habitats provides a home for a wide range of plants and animals.

Sinharaja is particularly rich in endemic species. Endemism is the presence of species that are found nowhere else on Earth.

In addition to its endemic species, Sinharaja is also home to a number of other important species, including the leopard (Panthera pardus) and the Asian elephant (Elephas maximus)

The biodiversity of Sinharaja rainforest is important for a number of reasons. First, it provides a home for a wide range of plants and animals. Second, it provides a number of important ecosystem services, such as water purification, climate regulation, and soil conservation. Third, it is a valuable source of genetic resources for potential future uses.