Dryobalanops rappa, commonly known as the Rapp's kapur, Rapp's ironwood, or locally known as Kapur Borneo or Kapur paya, is a species of tree in the Dipterocarpaceae family (Chudnoff, 1984). It is native to the island of Borneo, where it grows in coastal mixed peat swamp forest, on sandy beaches and clay, and rarely in kerangas forest, at altitudes of up to 900 m (Whitmore, 1998). The tree can reach heights of up to 55 meters (Chudnoff, 1984) and has a straight, cylindrical trunk with scaly, reddish-brown bark (Whitmore, 1998). This species is easily recognized from its crown which is copper-coloured (Wood & Meijer, 1964).

The leaves of Dryobalanops rappa are alternate and ovate-lanceolate in shape, with a glossy green color and a smooth, leathery texture (Chudnoff, 1984). They are typically about 10-15 cm long and have a pointed tip (Whitmore, 1998). The flowers of the tree are small and yellow, and are followed by small, round fruit containing seeds (Chudnoff, 1984).

In addition to its ecological and economic importance, Dryobalanops rappa also has cultural significance in many parts of Borneo. The tree is often planted around temples and other sacred sites and is considered to be a symbol of good fortune and prosperity (Whitmore, 1998). Despite its many uses and cultural significance, Dryobalanops rappa is threatened by habitat loss and degradation due to logging, agriculture, and other human activities (Chudnoff, 1984). Conservation efforts, such as the protection of natural habitats and the promotion of sustainable land use practices, are necessary to ensure the long-term survival of this species.