Nullarbor is a locality in the Australian state of South Australia located 295 km to the west of the town of Ceduna in the western part of the state immediately adjoining the border with Western Australia.

The name and extent of the locality was officially established on 26 April 2013 in respect to "the long established local name." Its name is derived from the use of "Nullarbor" in geographic features such as the Nullarbor Plain and protected areas such as the Nullarbor Regional Reserve.

Nullarbor is bounded in the west by the Western Australia - South Australian state border, in the south by the coastline adjoining the Great Australian Bight, to the east by the localities of Yalata and Yellabinna and to the north by the Trans-Australian Railway.

The land use within Nullarbor is concerned with the following protected areas which fully cover its extent - the Nullarbor Regional Reserve to the north of the locality, the Nullarbor National Park which occupies a strip running from the border and the Nullarbor Wilderness Protection Area which adjoins the coastline with the Great Australian Bight. Uses included tourism and research associated with the locality’s natural features, mineral exploration in the Regional Reserve, and use by indigenous communities for purposes such as cultural activities.

The Eyre Highway is the major road passing throughout the locality to Western Australia. Settlements located along the Highway include one known as "Nullarbor" at the eastern boundary of the locality and Border Village at the western boundary of the locality at the Western Australian border. These provide services for tourists and travellers such as accommodation and vehicle fuel.

Nullarbor is located within the federal Division of Grey, the state electoral districts of Flindersand Giles, and the unincorporated area of South Australia.

Marrawijinie Cave is cave located in the Australian state of South Australia within the gazetted locality of Nullarbor on the Nullarbor Plain.

This cave is open to the public but safety precautions should be taken before driving off the Eyre Highway. The entry is located approximately 10 km north of the Nullarbor Roadhouse along a rough track.

The main entry is a doline, a collapsed cave, another two entries are close by which is typical of the Nullarbor's karst topography. Hawks and Swallows use the caves as nesting sites.

One of the entries has hand stencils made from ochre drawn by Indigenous Australians on the walls.

Since June 2013, the cave has been located within the protected area known as the Nullarbor Wilderness Protection Area.