The Mary was a case heard by the United States Supreme Court in 1817. The dispute arose when two vessels, both named The Mary, collided off the coast of Massachusetts. Both ships were insured with different companies and each company sought to recover damages from the other for their respective losses. In its decision, the court held that where two vessels collide at sea due to negligence or fault on either side, there is no right of contribution between them as they are considered equal wrongdoers and therefore neither can seek compensation from one another. Furthermore, it was determined that if an insurance company pays out a claim due to such an incident then it has no recourse against any party involved in order to recoup those costs; instead they must bear this loss themselves. This ruling established important precedent regarding maritime collisions and liability for damages incurred during such events.

In The Mary, the Supreme Court was asked to decide whether a ship that had been seized by French privateers during the Quasi-War with France could be considered an enemy vessel. Justice Story wrote a dissenting opinion in which he argued that the seizure of The Mary violated international law and should not have occurred. He noted that while it is true that war gives belligerents certain rights over neutral vessels, those rights are limited and do not include seizing ships without cause or for purposes other than preventing them from aiding their own country's enemies. Furthermore, since there was no declaration of war between France and America at this time, any such seizures were illegal under both American and international law. Therefore, Justice Story concluded that The Mary should never have been taken as an enemy vessel in the first place and its owners should be compensated for their losses accordingly.