Admiralty law is a body of law governing navigation and shipping. Subjects that fall under the umbrella of Admiralty law include waters, navigation, shipping, commerce, seamen, wharves, towage, piers, docks, canals, insurance, canals, recreation, cruise ships and even piracy.

The United States Federal courts take their jurisdiction over Admiralty law from the Judiciary Act of 1789 and from the US Constitution. The US Congress regulates admiralty based in part on the commerce clause. Although Admiralty law in the US originally applied only to American tidal waters, it now extends to any navigable waters within the US used for interstate or foreign commerce. Therefore, Admiralty jurisdiction includes maritime matters not involving interstate commerce, such as recreational boating.

United States Admiralty law was derived from British admiralty courts. Admiralty law shares much in common with, but remains separate from, civil law.

Some points of Admiralty law:

Parties subject to admiralty cannot contract out of admiralty jurisdiction.

States may not infringe on admiralty jurisdiction.

In admiralty law, a ship's flag determines the source of law the ship is subject to.