A privateer was a privately owned ship whose captain had official permission from a government to attack and capture enemy vessels during wartime. Think of it as government-approved piracy: the ship's owner would get a special license called a “letter of marque” that said, “You can raid our enemy's ships, and we won't arrest you for it.”

Privateers were crucial in naval warfare from the 1500s through the early 1800s. Countries like England, France, and Spain used privateers to weaken their enemies' trade and military power without having to build huge, expensive navies. The privateer crews would keep much of the treasure and cargo they captured, which made privateering very profitable (and very dangerous).

The word privateer refers both to the ship itself and to the sailors who crewed it. Famous privateers like Sir Francis Drake attacked Spanish treasure ships on behalf of England, becoming wealthy and celebrated. During the American Revolution, American privateers captured hundreds of British supply ships, seriously disrupting British operations.

Privateering differed from regular piracy because privateers had legal authorization and were supposed to attack only enemy nations during wartime. Pirates, by contrast, attacked anyone and were considered criminals by all nations. When the war ended, a privateer's license expired, and continuing to raid ships after that would make you a pirate.