(This article is about the flag. For the rank, see Ensign (rank). For other uses, see Ensign (disambiguation).) Ensign is the national flag flown on a vessel to indicate nationality. The ensign is the largest flag, generally flown at the stern (rear) of the ship. Naval ensigns, used on warships, may be different from the civil ensign (merchant ships) or the yacht ensign (recreational boats). Large versions of naval ensigns called battle ensigns are used when a warship goes into battle.