Federal crimes are criminal offenses based on legislation (laws or statutes) enacted by the United States Congress and published in the United States Code (U.S.C.). Most crimes (murder, rape, assault, burglary, etc.) are prosecuted under state law (statutes) and are known as state law crimes. In contrast, crimes prosecuted under federal law are known as federal crimes.

Federal crimes generally involve a subject over which the United States Constitution gives the federal government—and more specifically, the U.S. Congress—the power or authority to legislate or make laws. This power or authority is also known as jurisdiction.

For example, the federal government (and not the states ) has the exclusive authority to print money and regulate its value. And because bank deposits are guaranteed (insured) by the federal government (FDIC) up to $250,000 per depositor, per FDIC-insured bank, and per ownership category, bank robbery is a federal crime (18 U.S.C. §2113). Examples of other federal crimes include tax evasion, wire fraud, mail fraud, immigration offenses, voting or electoral fraud, counterfeiting money, espionage (spying), and damaging or destroying mailboxes.

In Arizona, as in other states, federal crimes are offenses that fall under the jurisdiction of the federal government, as established by the United States Constitution and legislated by the U.S. Congress. These crimes are codified in the United States Code (U.S.C.) and are distinct from state crimes, which are prosecuted under Arizona state law. Federal jurisdiction typically covers activities that cross state lines, involve federal property or employees, or pertain to federal interests such as the regulation of currency, as in the case of counterfeiting, or the protection of federally insured banking institutions, as in the case of bank robbery (18 U.S.C. §2113). Other federal offenses include tax evasion, wire and mail fraud, immigration violations, and election fraud. Federal agencies such as the FBI, DEA, and ATF, in conjunction with the U.S. Attorney's Office, are responsible for the investigation and prosecution of federal crimes in Arizona.