Various rulers or governments of Europe, of Tonga and of Japan bestow or recognise the title of baron. In the British peerage system, barons rank lowest, coming after viscounts. A female of baronial rank has the honorific baroness. A baron may hold a barony (plural baronies).
The word baron derives from an Old French word baro ('man' in the sense of 'vassal'): Et quant ce virent li baron de l'ost, qui estoient herbergié d'autre part del port... ("And when the barons of the host [of fighting men at Constantinople] appeared, who were garrisoned in another part of the harbor...")
William the Conqueror introduced "baron" as a rank into England to distinguish the men who had pledged their loyalty to him (see Feudalism). Previously, in the Anglo-Saxon kingdom of England, the king's companions held the title of earls and in Scotland, the title of thane. All who held their barony "in chief of the king" (i.e. directly from William and his successors) became alike barones regis (barons of the king), bound to perform a stipulated service, and welcome to attend his council. Before long, the greatest of the nobles, especially in the marches, such as the Earls of Chester or the Bishops of Durham, might refer to their own tenants as "barons", where lesser magnates spoke simply of their "men" (homines).
Initially those who held land direct of the crown by military service, from earls downwards, all alike bore the title of baron, but under Henry II, the Dialogus de Scaccario already distinguishes greater or lesser baronies. Within a century of the Norman Conquest, as in Thomas Becket's case (1164), there arose the practice of sending to each greater baron a special summons to the council that evolved into the House of Lords, while the lesser barons, Magna Carta (1215) stipulated, would receive summons only in general, through the sheriffs. Thus appeared a definite distinction, which eventually had the effect of restricting to the greater barons the rights and privileges of peerage.
The King of England could create a new barony in one of two ways: by a writ of summons directing someone to Parliament, or by letters patent. Writs of summons featured in medieval times, but creation by letters patent has become the norm. Baronies thus no longer directly relate to land ownership.
Angela Georgina Burdett-Coutts became the first woman created baroness in her own right in 1871, by Queen Victoria.
In Scotland, the rank of baron refers to the holder of a feudal barony, which does relate to the feudal jurisdiction ower the territorial entity. But with the end of feudalism in Scotland, after 28th November 2004 the dignity of a Scottish Baron became a purely hereditary title of honour, ranking below all baronets and above all Clan Chiefs (who are not peers of the Realm).The Scots system does not have baronies as in England, but "Lordships of Parliament". Generally, the more modern baronies pass only to heirs male. However, in the cases of Scottish Lordships of Parliament and of English baronies by writ a daughter can inherit provided she has no brothers. In the English case, if there are multiple daughters, they jointly inherit the barony as coheirs, which then falls into abeyance until there is only one heir again.
In the late twentieth century Britain introduced the concept of non-hereditary life peers. All appointees to this distinction have taken place at the rank of baron, though in principle nothing prevents the creation of a life peerage of higher rank.
Normally one refers to or addresses Baron X as Lord X and his wife as Lady X. In the case of women granted life peerages in their own right, however, convention styles them as Baroness X rather than Lady X -- see for example Baroness Thatcher. The husband of a Baroness in her own right does not receive a style. Children of Barons and Baronesses in their own right, whether hereditary or for life, have the style The Honourable [Forename] [Surname]. After the death of the father or mother, the child may continue to use the style Honourable.
In the republics of continental Europe, the title of "Baron" retains a purely social prestige, with no particular political privileges. In Tonga, as opposed to the situations in Europe and in Japan, barons continue to hold and exercise significant political power.
Several communes in France have the name Baron :