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 Iowa, as in all states, federal crimes are offenses that are prosecuted under the authority of laws passed by the United States Congress, as opposed to state statutes. These crimes are codified in the United States Code (U.S.C.) and typically involve matters under federal jurisdiction, which is the legal authority granted to the federal government by the U.S. Constitution. Examples of federal crimes include offenses related to the federal government's exclusive powers, such as counterfeiting currency, bank robbery due to the federal insurance of bank deposits by the FDIC, and various forms of fraud (wire, mail) that cross state lines or involve federal agencies. Other federal offenses encompass immigration violations, tax evasion, and espionage. These crimes are investigated by federal agencies such as the FBI, DEA, and IRS, and are prosecuted by United States Attorneys in federal courts. While most common law crimes like murder and assault are handled by state courts in Iowa, when a crime violates federal law, it is handled by the federal court system, regardless of where the offense occurred.