Justiciar is the English form of the medieval Latin term or (meaning "judge" or "justice"). The Chief Justiciar was the king's chief minister, roughly equivalent to a modern Prime Minister of the United Kingdom.
The Justiciar of Ireland was an office established during the Anglo-Norman invasion of Ireland and was a key tool in its colonisation. Following the conquest of the Principality of Wales in the 13th century, the areas that became personal fiefs of the English monarchs were placed under the control of the Justiciar of North Wales and the Justiciar of South Wales.
A similar office was formed in Scotland, although there were usually two or three – the Justiciar of Scotia, the Justiciar of Lothian and, in the 13th century, the Justiciar of Galloway. These offices later evolved into a national one called Lord Justice-General. The modern title is Lord President of the Court of Session.
Similar positions existed in continental Europe, particularly in Norman Italy and in Sweden.
England
In Norman England, kings enlarged the scope of royal justice by delegating judicial authority to members of the (Latin for "king's court"). These were called justiciars. Henry I () appointed local justiciars to supervise a county or group of counties. It was not until the reign of Henry II (1154–1189) that the title was exclusively applied to the king's chief minister. While Flambard was probably the first to exercise the powers of a chief justiciar, he never held that rank officially. Nevertheless, he was described by contemporary chronicler Orderic Vitalis as a .
List of chief justiciars of England
{| class="wikitable"
!Name
!Term
!King(s)
|-
|Roger of Salisbury
|1102–1116?
|rowspan="3"|Henry I
|-
|Ralph Basset
|1116
|-
|Richard Basset (Justiciar)
|
|-
|Roger of Salisbury
|?–1139
|Stephen
|-
|Robert de Beaumont, 2nd Earl of Leicester
|1154–68 (jointly with Richard de Luci)
|rowspan="3"|Henry II
|-
|Richard de Luci
|1154–79
|-
|Ranulf de Glanville
|1180–89
|-
|William de Mandeville, 3rd Earl of Essex
|1189 (jointly with Hugh de Puiset)
| rowspan="5" |Richard I
|-
|Hugh de Puiset, Bishop of Durham
|December 1189 – April 1190
|-
|William Longchamp, Bishop of Ely
|1189–91
|-
|Walter de Coutances, Archbishop of Rouen
|1191–93
|-
|Hubert Walter, Archbishop of Canterbury
|1194–98
|-
|Geoffrey Fitz Peter, 1st Earl of Essex
|11 July 1198 – 14 October 1213
| rowspan="3" |John
|-
|Peter des Roches, Bishop of Winchester
|1213–1215
|-
|rowspan="2"|Hubert de Burgh, 1st Earl of Kent
|rowspan="2"|1215–1232
|-
|rowspan="5"|Henry III
|-
|Stephen de Segrave
|?–1234