The White Ensign or St George's Ensign is an ensign flown on British Royal Navy ships and shore establishments. It consists of a red St George's Cross on a white field with the Union Flag in the upper canton.

Royal Navy ships and submarines wear the White Ensign at all times when underway. The White Ensign may also be worn on a gaff, and may be shifted to the starboard yardarm when at sea. When alongside, the White Ensign is worn at the stern, with the Union Jack at the stem, during daylight hours.

The White Ensign is worn at the mastheads when Royal Navy ships are dressed on special occasions such as the Queen's birthday, and may be similarly be worn by foreign warships in British waters when dressed in honour of a British holiday or when firing a salute to British authorities.