Perjury, in law, a false statement made deliberately by a person under oath. Mistaken testimony believed to be true by the person testifying is not perjury. Neither is an answer that is truthful in itself but that does not give all the pertinent facts. Under common law, perjury was limited to testimony in court, but by statute it has been extended to many other proceedings. False statements made on income tax returns and false testimony given before legislative investigating committees are punishable as perjury.

Perjury is usually a felony, but is sometimes a misdemeanor. The penalty varies under different statutes. A person cannot be convicted of perjury on the testimony of a single witness; guilt must be proven beyond reasonable doubt.