The White Ensign, at one time called the St George's Ensign because of the simultaneous existence of a crossless version of the flag, is an ensign worn on British Royal Navy ships and shore establishments. It consists of a red St George's Cross on a white field, identical to the flag of England except with the Union Flag in the upper canton.

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.