The Justiciar of Lothian (in Norman-Latin, Justiciarus Laudonie) was an important legal office in the High Medieval Kingdom of Scotland.
The Justiciars of Lothian were responsible for the administration of royal justice in the province of Lothian, a much larger area than the modern Lothian, covering Scotland south of the Forth and Clyde, outwith Galloway, which had its own Justiciar of Galloway. The institution may date to the reign of King David I (died 1153), whose godson David Olifard was the first attested Justiciar. The Justiciars of Lothian, although not magnates of the stature of the typical Justiciar of Scotia, were significant landowners and not creatures of the kings.