Magellanica

Terra Australis
1570 map by Abraham Ortelius depicting "Terra Australis Nondum Cognita" as a large continent on the bottom of the map and also an Arctic continent
Type	Hypothetical continent
Notable locations	Patalis

Terra Australis (Latin for South Land) is a hypothetical continent first posited in antiquity and which appeared on maps between the 15th and 18th centuries. The existence of Terra Australis was not based on any survey or direct observation, but rather on the idea that continental land in the Northern Hemisphere should be balanced by land in the south. This theory of balancing land has been documented as early as the 5th century on maps by Macrobius, who uses the term Australis on his maps.

In the early 1800s, British explorer Matthew Flinders popularized the naming of Australia after Terra Australis, giving his rationale that there was "no probability" of finding any significant land mass anywhere more south than Australia. The continent that would come to be named Antarctica would be explored decades after Flinders' 1814 book on Australia, which he had titled A Voyage to Terra Australis, and after his naming switch had gained popularity.

Terra Australis was one of several names applied to the largest landmass of what is now known as the continent of Australia, after its European discovery. Other names for the hypothetical landmass have included Terra Australis Ignota, Terra Australis Incognita ("The unknown land of the South") or Terra Australis Nondum Cognita ("The Southern Land Not Yet Known"). Other names for the hypothetical continent have included Brasiliae Australis, Magallanica or Magellanica ("the land of Magellan"), La Australia del Espíritu Santo (Spanish: "the southern land of the Holy Spirit"), and La grande isle de Java (French: "the great island of Java"). Other names actually used for the continent were New Holland and Australia.