Lanjak-Entimau, a wildlife sanctuary of approximately 170,000 hectares in southwestern Sarawak, has been given priority for development as a Totally Protected Area. The Sanctuary had been gazetted in 1983, primarily as an Orang Utan reserve, but had remained relatively uncharted territory since that time.

This sanctuary comprises rugged and steeply dissected terrain with hills and ridges that are commonly over 300m. Steep slopes with narrow V-shaped valleys dominate the area.

The sanctuary has three peaks, namely: Bukit Lanjak (1,284m); Bukit Entimau (975m) and Gunong Spali (966m), which rise out of relatively low-lying country as an isolated peak. Comprises regosols, which are shallow soils overlying weathered rocks.

The region is an important water-catchment area and is drained by the Rivers Ensirieng, Mujok, Poi, Ngemah, Katibas, Bloh, Apoh and Kanowi (Kavanagh, 1982).