The Latin term terra nullius, meaning “land belonging to no person” is used to refer to lands not associated with a specific sovereign or government. While the term implies that the land is empty, in actuality it was often used to describe regions inhabited by indigenous peoples, such as Australia. Colonizing nations claimed that the land belonged to no one and therefore they had the right to occupy it.
This term has a loaded and complex history. In terms of the history of colonialism, terra nullius could be better thought of as a term used to describe an area that is not subject to a European-style government. A number of nations with complex social and political structures were occupied by European powers on the grounds that they were terra nullius, despite the demonstrable fact that people were already there and using the territory.
Indigenous groups in several regions of the world filed suits during the 20th century in attempts to restore title to their land or lay claim to land of particular importance to them, such as religious sites. These groups argued that the circumstances under which the land was taken were false, as colonizers claimed the land was not in use and wasn't subject to any government when this was not the case. Some of these suits were successful, restoring important sites to indigenous control.
This concept has also been used to literally describe land that belongs to no one, such as the no man's land found on the borders of some nations. In a few regions of the world, border disputes and redrawings have resulted in situations where there are strips of land that no one has laid claim to. Officially, the land belongs to no one and no government or entity considers the land its responsibility or property. Sections of Antarctica are often described as terra nullius, although by common agreement they are not exploited, as Antarctica is considered a resource for all of humanity.
In modern contexts, people occasionally use this term to describe land that does not appear to be subject to a government as discussed above. Because of the association with terra nullius and colonialism, this usage is not universal, and it is advisable to use this term with care. In the sense of land truly belonging to nobody, terra nullius is quite rare, as most human societies are reluctant to allow unclaimed land in their vicinity to lie fallow and unused.