An outlaw or bandit is a person living the lifestyle of outlawry; the word literally means "outside the law", by folk-etymology from the original meaning "laid outside" of the Old Norse word útlagi, from which the word outlaw was borrowed into English. In the common law of England, a judgment declaring someone an outlaw, known as a "Writ of Outlawry", was one of the harshest penalties in the legal system, since the outlaw could not use the legal system to protect himself if needed, such as from mob justice.

Though the judgment of outlawry is now obsolete (even though it inspired the pro forma Outlawries Bill which is still to this day introduced in the British House of Commons during the State Opening of Parliament), romanticised outlaws became stock characters in several fictional settings, particularly in Western movies. Thus, "outlaw" is still commonly used to mean those violating the law or, by extension, those living that lifestyle, whether actual criminals evading the law or those merely opposed to "law-and-order" notions of conformity and authority (such as the "outlaw country" music movement in the 1970s).

A feature of older legal systems

In British common law, an outlaw was a person who had defied the laws of the realm, by such acts as ignoring a summons to court, or fleeing instead of appearing to plead when charged with a crime. In the earlier law of Anglo-Saxon England, outlawry was also declared when a person committed a homicide and could not pay the weregild, the blood-money, due to the victim's kin. Outlawry also existed in other legal codes of the time, such as the ancient Norse and Icelandic legal code. These societies did not have any police force or prisons and criminal sentences were therefore restricted to either fines or outlawry.

To be declared an outlaw was to suffer a form of civil or social death. The outlaw was debarred from all civilized society. No one was allowed to give him food, shelter, or any other sort of support — to do so was to commit the crime of aiding and abetting, and to be in danger of the ban oneself. An outlaw might be killed with impunity; and it was not only lawful but meritorious to kill a thief flying from justice — to do so was not murder. A man who slew a thief was expected to declare the fact without delay, otherwise the dead man's kindred might clear his name by their oath and require the slayer to pay weregild as for a true man Because the outlaw has defied civil society, that society was quit of any obligations to the outlaw —outlaws had no civil rights, could not sue in any court on any cause of action, though they were themselves personally liable.

In the context of criminal law, outlawry faded not so much by legal changes as by the greater population density of the country, which made it harder for wanted fugitives to evade capture; and by the international adoption of extradition pacts. In the civil context, outlawry became obsolescent in civil procedure by reforms that no longer required summoned defendants to appear and plead. Still, the possibility of being declared an outlaw for derelictions of civil duty continued to exist in English law until 1879 and in Scots law until the late 1940s. The Third Reich made extensive use of the concept. Prior to the Nuremberg Trials, the British jurist Lord Chancellor Lord Simon attempted to resurrect the concept of outlawry in order to provide for summary executions of captured Nazi war criminals. Although Simon's point of view was supported by Winston Churchill, American and Soviet attorneys insisted on a trial, and he was thus overruled.