The Australian white ensign is a naval ensign used by ships of the Royal Australian Navy (RAN) from 1967 onwards. From the formation of the RAN until 1967, Australian warships used the British white ensign as their ensign. However, this led to situations where Australian vessels were mistaken for British ships, and when Australia became involved in the Vietnam War, the RAN was effectively fighting under the flag of another, uninvolved nation. Proposals were made in 1965 for a unique Australian ensign, which was approved in 1966, and entered use in 1967.

The ensign is a maritime flag that is used for the national identification of a ship. The ensign is the largest flag, generally flown at the stern (rear) of the ship while in port. In ports, depending on the ship's origin, it is sometimes identical with a jack on the bow of the ship. Jacks are more common on warships than on merchant ships.