Perjury is the criminal offense of making a false statement under oath—verbally or in writing—that the witness knows to be false and that is material to the proceeding in which the statement is made. And suborning perjury or subornation of perjury is the criminal offense of procuring the perjury of another person.

Perjury is a criminal offense under both state and federal laws and may be prosecuted as a misdemeanor or as a felony offense, depending on the state or federal jurisdiction, and whether there are any aggravating factors that increase the seriousness of the crime. Perjury laws are located in state statutes—often in the penal or criminal code—and the federal perjury law is located in the United States Code at 18 U.S.C. §1621.

In Washington State, perjury is defined as making a false statement under oath, whether verbally or in writing, which the person knows to be untrue and which is material to the legal proceeding at hand. This is codified in the Revised Code of Washington (RCW) under RCW 9A.72.020 and RCW 9A.72.030. Perjury can be prosecuted as either a Class B or Class C felony, depending on the circumstances, with Class B felonies carrying more severe penalties. Subornation of perjury, which involves persuading or inducing another person to commit perjury, is also a criminal offense and is treated with similar severity as perjury itself. At the federal level, perjury is governed by 18 U.S.C. §1621, and like state law, it criminalizes the act of willfully making false statements under oath in federal proceedings. The federal statute also allows for the prosecution of individuals who commit perjury, with the potential for significant fines and imprisonment.