What sea is northwest of Australia?

The Timor Sea lies to the north-west of Australia, between the Australian mainland and the island of Timor. It covers about 610,000 square kilometres and is generally considered part of the Indian Ocean, though some classifications include it as part of the western Pacific.

The Timor Sea borders the Northern Territory and the Kimberley coast of Western Australia. It is shallow over much of its area because it sits on the broad Sahul Shelf, the submerged continental shelf that connects Australia to New Guinea and once formed dry land during ice age low sea levels. The Sahul landmass enabled the original migration of Aboriginal ancestors from Asia at least 65,000 years ago.

The Timor Sea is rich in oil and gas. Major fields include Bayu-Undan, Greater Sunrise, Ichthys, Prelude, and Browse. Bayu-Undan supplied gas to a liquefied natural gas plant in Darwin from 2006 until reserves were exhausted in 2023. Greater Sunrise, the largest undeveloped resource, is the subject of long-running negotiations between Australia and Timor-Leste, after the International Court of Arbitration in 2018 redrew the maritime boundary in Timor-Leste's favour following the disclosure that Australia had bugged Timor-Leste's cabinet during 2004 boundary talks.

The Timor Sea is also a major route for Australian Border Force patrols and the Royal Australian Navy, monitoring for unauthorised arrivals from Indonesia, illegal fishing, and people-smuggling vessels. Operation Sovereign Borders, launched in 2013, led to a sharp reduction in irregular maritime arrivals across the Timor and Arafura seas. Cyclones from the sea regularly affect the north coast, with Cyclone Tracy in 1974 the most devastating in Australian history.