The primary national flag hoisted by a ship, typically flown from a staff at the stern or from the main mast when underway. It legally identifies the vessel's nationality and jurisdiction under maritime law. Different countries often have specific civilian, naval, and state ensigns rather than using their standard national flag.
Heard on the job
Make sure the red ensign is hoisted before we enter territorial waters.
Insider tip
In many maritime traditions, the ensign is hoisted at 0800 and lowered at sunset while in port, but flown continuously when at sea.