The Gulf of Carpentaria is a vast, shallow sea surrounded on three sides by northern Australia and bounded in the north by the Arafura Sea - the body of water that lies between Australia and New Guinea. The land that borders the Gulf is generally low-lying and flat. The Northern Territory is found at the top end of the Gulf; to the west is Arnhem Land and Groote Eylandt, the largest island in the Gulf. The Cape York Peninsula and Torres Strait which joins the Gulf to the Coral Sea are located to the east and the area to the south, where the Cape York Peninsula that is part of Queensland is found is known as the Gulf Country.

The Gulf covers an area of about 300,000 square kilometres and is 700 kilometres long from north to south, 590 kilometres wide at the mouth, and further south it is 675 kilometres wide. The general depth of the Gulf is between 55 and 66 metres with a maximum depth of 82 metres. Several major rivers flow into the Gulf, at the top end, the Roper River, the Walker River and Wilton River; the Cox River, Calvert River, Leichhardt River, McArthur River, Flinders River, Norman River and the Gilbert River drain into the Gulf Country; and various rivers including Smithburne River, Mitchell River, Alice River, Staaten River, Mission River, Wenlock River and Archer River flow from the Cape York Peninsula into the Gulf.

The climate of the Gulf is hot and humid with two seasons in a year, a dry season from about April until November and a wet season that lasts from December to March. During the wet season, many low-lying areas are flooded. The Gulf is also susceptible to tropical cyclones from November and April, with an average of three cyclones each year. In September and October the phenomenon known as the Morning Glory cloud appears in the Southern Gulf and the best vantage point to view it is in the Burketown area shortly after dawn.