Today the Northern Territory's land borders are defined to the west by the 129° east longitude (129° east) with Western Australia, to the south by the 26th parallel south latitude (26° south) with South Australia and to the east by 138° east longitude (138° east) with Queensland; however, this is not where all borders are actually marked on the ground.
The Northern Territory boundaries are shared with the West Australian border, the South Australian border, and the Queensland border.