Federal pardons in the United States are granted only by the U.S. president, pursuant to authority under the U.S. Constitution to grant "reprieves and pardons for offenses against the United States". Pardons extend to all federal criminal offenses, except in cases of impeachment, and entail various forms of clemency, including commuting or postponing a sentence, remitting a fine or restitution, delaying the imposition of a punishment, and providing amnesty to an entire group or class of individuals. The pardon power extends to cases involving courts-martial against members of the United States Armed Forces, including the Army, the Navy, the Air Force, the Marine Corps, the Coast Guard, and the Space Force.

The president may grant pardons on his or her own accord or in response to requests made through the U.S. Department of Justice's Office of the Pardon Attorney. The Pardon Attorney investigates and reviews applications for clemency but serves only an advisory role; the president may disregard the findings or bypass the office altogether. The pardon power is considered "plenary" and thus generally cannot be restricted or modified by Congress or the judiciary. In Ex parte Garland (1867), the U.S. Supreme Court confirmed the "unlimited" nature of federal pardons (except for impeachment cases) and broadened its scope to include offenses for which legal proceedings have not been initiated. Pardons have been used for presumptive cases, most notably when President Gerald Ford pardoned Richard Nixon over any possible crimes connected with the Watergate scandal; the legal effect of such "open pardons" has not been determined by the judiciary.

In Burdick v. United States (1915), the Supreme Court held that a pardon does not take effect if the defendant does not accept it. In 2021, the Tenth Circuit Court of Appeals ruled that acceptance of a pardon does not constitute a legal confession of guilt, recognizing the Supreme Court's earlier language as dicta.

The pardon power of the president is based on Article II, Section 2, Clause 1 of the U.S. Constitution, which provides:

The President ... shall have Power to grant Reprieves and Pardons for Offenses against the United States, except in Cases of impeachment.

The U.S. Supreme Court has interpreted the provision to include the power to grant pardons, conditional pardons, commutations of sentence, conditional commutations of sentence, remissions of fines and forfeitures, respites and amnesties.

The concept of governments having the authority to provide relief from criminal punishment has deep and broader historical roots, including in ancient Jewish, Greek, and Roman legal principles and practice. The U.S. Constitution's pardon power originated from longstanding English tradition, which permitted the monarch to exercise the "royal prerogative of mercy" to withdraw or provide alternatives to death sentences. The first known prerogative of mercy was issued by King Ine of Wessex (688–725), and during the reign of King Henry VIII (1509–1547), it was formally declared by parliament as an exclusive right of the Crown. By the 18th century, the power had been restricted by parliament, enabling it to address potential abuses, but retained its broad application, including in the American colonies. The framers of the U.S. Constitution were directly influenced by the English practice.

Alexander Hamilton defended the pardon power in The Federalist Papers, particularly in Federalist No. 74, where he argued that such a power should be as little as possible fettered or embarrassed to ensure easy access to exceptions in favour of unfortunate guilt. Hamilton also argued that placing power solely with the President would lead to its most beneficial exercise, as a single person would be a more eligible dispenser of the mercy of the government than a body of men who might often encourage each other in an act of obduracy, and might be less sensible to the apprehension of suspicion or censure for an injudicious or affected clemency.