United States Attorneys (also known as federal prosecutors and, historically, as United States District Attorneys) represent the United States federal government in United States district court and United States court of appeals. There are 93 U.S. Attorneys stationed throughout the United States, Puerto Rico, the U.S. Virgin Islands, Guam, and the Northern Mariana Islands. One U.S. Attorney is assigned to each of the judicial districts, with the exception of Guam and the Northern Mariana Islands where a single U.S. Attorney serves both districts. Each U.S. Attorney is the chief federal law enforcement officer within his or her particular jurisdiction, acting under the guidance of the United States Attorneys' Manual. They supervise district offices of as many as 350 assistant U.S. attorneys, with as many as 350 more support personnel. U.S. Attorneys and their offices are part of the Department of Justice. U.S. Attorneys receive oversight, supervision and administrative support services through the Justice Department's Executive Office for United States Attorneys. Selected U.S. Attorneys participate in the Attorney General's Advisory Committee of United States Attorneys.

The Office of the United States Attorney was created by the Judiciary Act of 1789, along with the office of Attorney General. The same act also specified the structure of the Supreme Court of the United States and established inferior courts making up the United States Federal Judiciary, including a district court system. Thus, the office of U.S. Attorney is older than the Department of Justice. The Judiciary Act of 1789 provided for the appointment in each judicial district of a "Person learned in the law to act as attorney for the United States...whose duty it shall be to prosecute in each district all delinquents for crimes and offenses cognizable under the authority of the United States, and all civil actions in which the United States shall be concerned..." Prior to the existence of the Department of Justice, the U.S. attorneys were independent of the Attorney General, and did not come under the AG's supervision and authority until 1870, with the creation of the Department of Justice.

The U.S. Attorney is appointed by the President of the United States for a term of four years, with appointments subject to confirmation by the Senate. A U.S. Attorney shall continue in office, beyond the appointed term, until a successor is appointed and qualified. By law, each United States attorney is subject to removal by the President. The Attorney General has had the authority since 1986 to appoint interim U.S. Attorneys to fill a vacancy.