Lynch law is an extralegal means of maintaining the established social order.

The term is said to originate from the career of Colonel Charles Lynch, an officer on the Patriot side of the American Revolutionary War, who applied it to Tories and criminal offenders alike. His favoured method was death by hanging, giving his activities seeming legitimacy as hanging was the form of capital punishment then generally called for by law.

The unauthorized hangings committed by Lynch and his followers continued to be duplicated by others in the U.S. and later, elsewhere, after the war and became the basis for the English word "lynching", which is both a verb describing the actual act and a noun as well. The term "lynch law" came in to general use as a description of efforts to maintain the established order either by the use of actual lynchings against those who would change it, or even their mere threat, which often became a sufficent motive to silence activists and critics.

Famous utilizers of lynch law in the U.S. included the San Francisco, California-based "Committee of Vigilance", which used lynch law tactics to maintain order in San Francisco in the 19th century after its members had decided that the traditional, legal system of justice was failing them, and saloonkeeper "Judge" Roy Bean, of roughly the same period, who, apparently without any authorization from Texas state officials, declared himself to be the "Law West of the Pecos", and often ordered the hanging of those he determined to be offenders from the "courtroom" in his saloon.

Lynch law is sometimes justified by its supporters as the administration of justice without the delays and inefficencies inherent in the legal system; in this way it echoes the Reign of Terror during the French Revolution, which was justified by the statement, "Terror is nothing more than Justice, swift and certain." The fact that lynch law victims were quite frequently innocent of their alleged offenses turned public opinion against it, even in the South where it was frequently employed by supporters of Jim Crow, until today it is largely no longer practiced. Most persons today who are the vicitims of vigilantism are murdered by more conventional means such as shooting or stabbing, and improvments in jail and prison security have lessened the once-common practice of the extra-legal hangings of those awaiting trial or those who were sentenced to prison terms when popular opinion was generally in favor of capital punishment for them.