The Navy traces its origins to the Continental Navy, which was established during the American Revolutionary War and was essentially disbanded as a separate entity shortly thereafter. The United States Constitution provided the legal basis for a military force by giving Congress the power "to provide and maintain a navy".

Depredations against American shipping by Barbary Coast pirates in the Mediterranean Sea spurred Congress to employ this power by passing the Naval Act of 1794 ordering the construction and manning of six frigates. These ships were used to end most pirate activity off the Barbary Coast. In the twentieth century American blue-water navy capability was demonstrated by the 1907–1909 world tour of the Great White Fleet.

The 21st century United States Navy maintains a sizable global presence, deploying in such areas as East Asia, the Mediterranean, and the Middle East. It is a blue water navy with the ability to project force onto the littoral regions of the world, engage in forward areas during peacetime, and rapidly respond to regional crises, making it an active player in American foreign and defense policy.

The Navy is administratively managed by the Department of the Navy, which is headed by the civilian Secretary of the Navy. The Department of the Navy is itself a division of the Department of Defense, which is headed by the Secretary of Defense. Traditionally, the highest ranking Naval officer is the Chief of Naval Operations, Admiral Gary Roughead. However, today the highest ranking Naval Officer is the Chairman of the Joint Chiefs of Staff, Admiral Michael Mullen.

From the New Recruits Handbook:

The United States Navy serves as a seaborne branch of the Military of the United States. 10 U.S.C. § 5062 prescribes the navy's three primary areas of responsibility:

U.S. Navy training manuals state the mission of the U.S armed forces is "to prepare and conduct prompt and sustained combat operations in support of the national interest". As part of that establishment, the U.S. Navy's functions comprise sea control, power projection and nuclear deterrence, in addition to "sealift" duties.

In the early stages of the American Revolutionary War, the establishment of an official navy was an issue of debate among the members of the Continental Congress. Supporters argued that a navy would protect shipping, defend the coast, and make it easier to seek out support from foreign countries. Detractors countered that challenging the British Royal Navy, then the world's preeminent naval power, was a foolish undertaking.

Commander in Chief George Washington commissioned seven ocean-going cruisers to interdict British supply ships, and reported the captures to the Congress. This effectively ended the debate in Congress as to whether or not to "provoke" the British by establishing a Navy as Washington's ships had already captured British ships, somewhat a provocation.

While Congress deliberated, it received word that two unarmed British supply ships from England were heading towards Quebec without escort. A plan was drawn up to intercept the ships—however, the armed vessels to be used were owned not by Congress, but by individual colonies. Of greater significance, then, was an additional plan to equip two ships that would operate under the direct authority of Congress to capture British supply ships. This was not carried out until 13 October 1775, when George Washington announced that he had taken command of three armed schooners under Continental authority to intercept any British supply ships near Massachusetts. With the revelation that vessels were already sailing under Continental control, the decision to add two more was made easier; the resolution was adopted and 13 October would later become known as the U.S. Navy's official birthday.