This thesis examines the appointment of the Commissaries of Edinburgh, the court over which they presided, and their consistorial jurisdiction during the era of the Scottish Reformation. It is argued that the Commissaries of Edinburgh were appointed by Mary, Queen of Scots, in February 1563/4 as a temporary measure following the suppression of the courts of the Catholic Church in Scotland during the Wars of the Congregation. The Commissaries’ jurisdiction was substantially that of the pre-Reformation Officials centralized into a national jurisdiction administered from Edinburgh. The Commissaries of Edinburgh’s jurisdictional relations with the inferior Commissaries, the Lords of Council and Session, the suppressed courts of the Catholic Church and the Lords Interpreters of the Law of Oblivion are examined, whilst their relations with the tribunals of the Protestant Kirk are given particular attention. The thesis argues that despite the complex constitutional, legal and religious legacy of the spiritual jurisdiction in Scotland, the Commissaries and Kirk achieved a high degree of jurisdictional harmony, despite occasional conflicts. The Commissaries continued to administer the Canon law of the medieval Church in consistorial matters, with the prominent exception of the innovation introduced into Scotland by the Protestant Kirk from 1559 concerning divorce and remarriage on the grounds of adultery. Through an analysis of sentences and decreets pronounced by pre-Reformation Officials, the Commissaries of Edinburgh, and the tribunals of the Protestant Kirk, it is argued that this reform was essentially a reform of divorce a mensa et thoro using concepts and formulas borrowed from pre- Reformation sentences of annulment. The result was a type of divorce unique to Scotland, where the innocent party was immediately freed to remarry, whilst the guilty party remained bound to the failed marriage until freed to remarry by the death of their innocent spouse. An analysis of consistorial litigation before the Commissaries of Edinburgh is used to explain and illustrate the Romano-canonical procedure used in their court and the documentation generated during litigation. Litigants’ gender, domicile and social status are also analysed, together with their use of procurators and the expenses incurred during litigation.