The Oenpelli python or Oenpelli rock python (Simalia oenpelliensis or Nyctophilopython oenpelliensis) is a species of large snake in the family Pythonidae. The species is endemic to the sandstone massif area of the western Arnhem Land region in the Northern Territory of Australia. There are no subspecies that are recognised as being valid. It has been called the rarest python in the world. Two notable characteristics of the species are the unusually large size of its eggs and its ability to change colour. It is the longest snake native to the Northern Territory.