Nepenthes rajah is an insectivorous pitcher plant species of the monotypic Nepenthaceae family. It is endemic to Mount Kinabalu and neighbouring Mount Tambuyukon in Sabah, Malaysian Borneo. N. rajah grows exclusively on serpentine substrates at an altitude of 1500 to 2650 m a.s.l., particularly in areas of seeping ground water, where the soil is loose and permanently moist. Due to its localised distribution, N. rajah is classified as an endangered species by the IUCN and listed on CITES Appendix I. N. rajah was first collected by Hugh Low in 1858. It was described the following year by Joseph Dalton Hooker, who named it after James Brooke, the first White Rajah of Sarawak. Since being introduced into cultivation in 1881, N. rajah has always been a much sought-after species. For a long time, it was a plant seldom seen in private collections due to its rarity, price, and specialised growing requirements. Recent advances in tissue culture technology have resulted in prices falling dramatically, and N. rajah is now relatively widespread in cultivation. N. rajah has giant urn-shaped traps, which can grow up to 35 cm high and 18 cm wide. These are capable of holding 3.5 litres of water and in excess of 2.5 litres of digestive fluid, making them probably the largest in the genus by volume. Another characteristic morphological feature of N. rajah is the peltate leaf attachment of the lamina and tendril, which is present in only a few other species. N. rajah is known to occasionally trap vertebrates including small mammals. Insects, and particularly ants, comprise the majority of prey in both aerial and terrestrial pitchers.