Australia II is an Australian 12-metre-class America's Cup challenge racing yacht that was launched in 1982 and won the 1983 America's Cup for the Royal Perth Yacht Club. Skippered by John Bertrand, she was the first successful Cup challenger, ending a 132-year tenure by the New York Yacht Club.

The 12 Metre class is a rating class for racing sailboats that are designed to the International rule. It enables fair competition between boats that rate in the class whilst retaining the freedom to experiment with the details of their designs. The designation "12 Metre" does not refer to any single measurement on the boat, and is not referencing the vessels overall length, rather, measures the sum of the components directed by the formula which governs design and construction parameters. Typically 12 Metre class boats range from 65 to 75 feet in length overall; they are most often sloop-rigged, with masts roughly 85 feet tall.