The Australia II is a 12-metre class yacht, and the first successful challenger for the America's Cup after 132 years.

Designed by Ben Lexcen, built by Steve Ward, owned by Alan Bond and helmed by John Bertrand. Australia II featured an innovative winged keel design developed by Lexcen which helped to make it very fast and manoeuvrable in many conditions and was the most interesting design feature of the boat. During the summer of 1983, as selection trials took place for the Cup defence that autumn, the New York Yacht Club challenged the legality of the keel design, but it was ruled to be legal. Despite being the first 12 metre to sport the new design, Australia II was not the first boat to have a winged keel, though its success did much to make the concept popular.

Australia II sported much other new technology which also contributed to her success, including her radical vertical sail designs, all kevlar running rigging and lightweight carbon fibre boom. John Bertrand and his crew trained intensively and were able to perform at the highest levels under the pressure of this historic match up.