An ensign is the lowest-ranking officer in the United States Navy or Coast Guard, similar to how a second lieutenant is the lowest officer rank in the Army. When someone graduates from the Naval Academy or completes officer training, they become an ensign and begin leading sailors on ships or at shore stations. Even though they're new officers, ensigns have significant responsibilities: they might navigate a ship, manage a division of sailors, or oversee important equipment.

The word also refers to a flag, especially one flown on a ship to show what country it belongs to. When you see a warship with the American flag flying from its mast, that flag is the ship's ensign. In the age of sailing ships, the ensign helped everyone identify whether an approaching vessel was friend or foe. Different countries have distinctive naval ensigns: Britain's Royal Navy flies the White Ensign, while merchant ships often fly different flags from military vessels.