The United States Maritime Administration (MARAD) is an agency of the United States Department of Transportation. MARAD administers financial programs to develop, promote, and operate the U.S. Maritime Service and the U.S. Merchant Marine. In addition it conducts research and development activities in the maritime field; regulates the transfer of U.S. documented vessels to foreign registries; maintains equipment, shipyard facilities, and reserve fleets of Government-owned ships essential for national defense.

Its programs promote the use of waterborne transportation and its seamless integration with other segments of the transportation system, and the viability of the U.S. merchant marine. The Maritime Administration works in many areas involving ships and shipping, shipbuilding, port operations, vessel operations, national security, environment, and safety. The Maritime Administration is also charged with maintaining the health of the merchant marine, since commercial mariners, vessels, and intermodal facilities are vital for supporting national security, and so the agency provides support and information for current mariners, extensive support for educating future mariners, and programs to educate America's young people about the vital role the maritime industry plays in the lives of all Americans.

MARAD also maintains the National Defense Reserve Fleet (NDRF) as a ready source of ships for use during national emergencies and logistically supporting the military when needed.