Flagship

A flagship is a vessel used by the commanding officer of a group of military ships. The name comes from a Pre Astro Terran custom of its commander, characteristically a flag officer, flying a distinguishing flag. Used more loosely, it is the lead ship in a fleet of vessels, typically the first, largest, fastest, most heavily armed, or best known.

For the specific case of the flagships in the Union Navy see Fleet Flagship.