Macassan trepangers from the southwest corner of Sulawesi (formerly Cele bes) visited the coast of northern Australia for hundreds of years to fish for trepang (also known as sea cucumber or "sandfish"), a marine invertebrate prized for its culinary and medicinal values in Chinese markets. These visits have left their mark on the people of Northern Australia — in language, art, economy and even genetics in the descendants of both Macassan and Australian ancestors that are now found on both sides of the Arafura and Banda Seas.
The trade began to dwindle toward the end of the 19th century due to the imposition of customs duties and licence fees by Australian governments that made it unviable, and after the introduction of legislation to protect Australia's "territorial integrity", the last Macassan prau left Arnhem Land in 1906. Demand for trepang may have also dropped off due to unrest in China at the time.
Matthew Flinders in his circumnavigation of Australia in 1803 met the Macassan trading fleet near present day Nhulunbuy, an encounter that led to the establishment of settlements on Melville Island and the Coburg Peninsula.
Remains of some of these processing plants from the 18th and 19th centuries can still be found at Port Essington, Anuru Bay and Groote Eylandt, along with stands of tamarind trees.
The Macassans exchanged goods such as cloth, tobacco, knives, rice and alcohol for the right to fish in Aboriginal waters, and to employ Aboriginal labour. Such products brought with them new opportunities as well as new challenges, such as the dangerous combination of knives and alcohol.
Some Yolngu communities of Arnhem land re-figured their economies from being largely land-based to largely sea-based with the introduction of Macassan technologies such as dug-out canoes. These seaworthy boats, unlike their traditional bark canoes, allowed Yolngu to fish the ocean for dugongs and turtles.
Some Aboriginal workers willingly accompanied the Macassans back to their homeland across the Arafura Sea. The Yolngu people also remember with grief the abductions and trading of Yolngu women, and the introduction of smallpox, which was epidemic in the islands east of Java at the time.
A Macassan pidgin became a lingua franca along the north coast, not just between Macassans and Aboriginal people, but also between different Aboriginal groups, who were brought into greater contact with each other by the seafaring Macassan culture. Words from the Macassan language can still be found in Aboriginal language varieties of the north coast; examples include rupiah (money), jama (work), and balanda (white person), which originally came to the Macassan language from the Dutch, "Hollander". Some of the goods traded by the Macassans spread far across the country, even to the south.
The Macassans may have also been the first to bring Islam to Australia.