Nepenthes rajah was first described in 1859.
The plant was collected on Mount Kinabalu in Borneo by Hugh Low in 1858. Joseph Dalton Hooker formally described it the following year, establishing the scientific name Nepenthes rajah. The specific epithet refers to James Brooke, the first White Rajah of Sarawak.
N. rajah is endemic to Mount Kinabalu and nearby Mount Tambuyukon in Sabah, Malaysian Borneo. It grows in wet, nutrient-poor serpentine soils at high elevations and is famous for its enormous urn-shaped pitchers.
A common mix-up is confusing the collection date with the description date: 1858 marks Low’s collection, while 1859 marks Hooker’s formal publication. The species later entered cultivation in 1881, after a collecting expedition for the Veitch Nurseries.