Arson is the crime of willfully and deliberately setting fire to or charring property. Although the act of arson typically involves buildings, the term can also refer to the intentional burning of other things, such as motor vehicles, watercraft, or forests. The crime is typically classified as a felony, with instances involving a greater degree of risk to human life or property carrying a stricter penalty. Arson which results in death can be further prosecuted as manslaughter or murder. A common motive for arson is to commit insurance fraud. In such cases, a person destroys their own property by burning it and then lies about the cause in order to collect against their insurance policy.

A person who commits arson is referred to as an arsonist, or a serial arsonist if arson has been committed several times. Arsonists normally use an accelerant (such as gasoline or kerosene) to ignite, propel and directionalize fires, and the detection and identification of ignitable liquid residues (ILRs) is an important part of fire investigations. Pyromania is an impulse control disorder characterized by the pathological setting of fires. Most acts of arson are not committed by pyromaniacs.