crime commonly defined by statute as the willful or malicious damage or destruction of property by means of fire or explosion. In English common law, arson referred to the burning of another person's dwellings under circumstances that endangered human life. Modern statutes have expanded this definition so that arson now includes the wrongful burning of any public or private property.

Most jurisdictions have divided arson statutes into two or more degrees, reserving the heavier punishments for burnings that pose a danger to human life. Such acts generally include the burning of vehicles, bridges, and forests as well as habitable dwellings (e.g., houses, stores, office buildings, and factories). In nearly all countries, an arsonist may be prosecuted for murder if someone dies as a result of the act, even if the intention to kill is absent. Some jurisdictions (e.g., Germany and some U.S. (United States) states) also impose a higher penalty for arson committed for the purpose of concealing or destroying evidence of another crime.

It can be arson to burn personal property as well as real estate. Statutes also have forbidden burnings caused by incendiary devices. By contrast, a fire caused by accident or ordinary carelessness is not arson, because criminal intent is lacking. Nonetheless, reckless activity—or burning without regard to consequences—can result in an arson conviction.

An arsonist may act from a variety of different motives, including rage, jealousy, profit (e.g., burnings undertaken to commit insurance fraud), and the desire to conceal or destroy evidence. Persons suffering from pyromania have a pathological and uncontrollable urge to set fires.