Sahul Shelf in the context of "Sunda Shelf"

The continent of Australia, sometimes known in technical contexts as Sahul (/səˈhuːl/), Australia-New Guinea, Australinea, or Meganesia to distinguish it from the country of Australia, is located within the Southern and Eastern hemispheres, near the Maritime Southeast Asia. The continent includes mainland Australia, Tasmania, the island of New Guinea (Papua New Guinea and Western New Guinea), the Aru Islands, the Ashmore and Cartier Islands, most of the Coral Sea Islands, and some other nearby islands. Situated in the geographical region of Oceania, more specifically in the subregion of Australasia, Australia is the smallest of the seven traditional continents.

The continent includes a continental shelf overlain by shallow seas which divide it into several landmasses—the Arafura Sea and Torres Strait between mainland Australia and New Guinea, and Bass Strait between mainland Australia and Tasmania. When sea levels were lower during the Pleistocene ice age, including the Last Glacial Maximum about 18,000 BC, they were connected by dry land into the combined landmass of Sahul. The name "Sahul" derives from the Sahul Shelf, which is a part of the continental shelf of the Australian continent. During the past 18,000 to 10,000 years, rising sea levels overflowed the lowlands and separated the continent into today's low-lying arid to semi-arid mainland and the two mountainous islands of New Guinea and Tasmania. With a total land area of 8.56 million square kilometres (3,310,000 sq mi), the Australian continent is the smallest, lowest, flattest, and second-driest continent (after Antarctica) on Earth. As the country of Australia is mostly on a single landmass, and comprises most of the continent, it is sometimes informally referred to as an island continent, surrounded by oceans.

Wallacea /wɒˈleɪsiə/ is a biogeographical designation for a group of mainly Indonesian islands separated by deep-water straits from the Asian and Australian continental shelves. Wallacea includes Sulawesi, the largest island in the group, as well as Lombok, Sumbawa, Flores, Sumba, and Timor. The islands of Wallacea lie between the Sunda Shelf (the Malay Peninsula, Sumatra, Borneo, and Java) to the west, and the Sahul Shelf, including Australia, New Guinea, and Maluku islands to the south and east. The total land area of Wallacea is 347,000 km (134,000 sq mi).

The Gulf of Carpentaria is a sea off the northern coast of Australia. It is enclosed on three sides by northern Australia and bounded on the north by the eastern Arafura Sea, which separates Australia and New Guinea. The northern boundary is generally defined as a line from Slade Point, Queensland (the northwestern corner of Cape York Peninsula) in the northeast, to Cape Arnhem on the Gove Peninsula, Northern Territory (the easternmost point of Arnhem Land), in the west.

At its mouth, the Gulf is 590 km (370 mi) wide, and further south, 675 km (420 mi). The north–south length exceeds 700 km (430 mi). It covers a water area of about 300,000 km (120,000 sq mi). The general depth is between 55 and 66 metres (30 and 36 fathoms) with a maximum depth of 69 metres (38 fathoms). The tidal range in the Gulf of Carpentaria is between two and three metres (6.5 and 10 ft). The Gulf and adjacent Sahul Shelf were dry land at the peak of the last ice age 18,000 years ago when global sea level was around 120 m (390 ft) below its present position. At that time a large, shallow lake occupied the centre of what is now the Gulf. The Gulf hosts a submerged coral reef province that was only recognised in 2004.