Founded in 1278 by a treaty between the bishop of Urgell and the Count of Foix, this unique diarchical arrangement has persisted through the Middle Ages to the present.

In 1812–13, the First French Empire under Napoleon annexed Catalonia and divided it into four départements, with Andorra forming part of the district of Puigcerdà (department of Sègre).

[9] Though initially enjoying some support within Andorra's political establishment, he was ultimately arrested by Spanish authorities on 20 July 1934 after declaring war on the Bishop of Urgell (who had refused to relinquish his own claim to the principality).

In March 1993, a Constitution was approved by a vote of the Andorran people and signed into law by the two reigning co-princes at the time: Bishop Joan Martí Alanis and President François Mitterrand.

[11] In 2014, Joan Enric Vives i Sicília said that he would abdicate as bishop of Urgell and co-prince of Andorra if the Andorran Parliament passed a law legalizing abortion.

The constitution establishes Andorra as a "parliamentary coprincipality",[13] providing for the Bishop of Urgell and the president of France to serve together as joint heads of state.

[20] Certain treaties require the participation of the co-princes (or their designated representatives) in their negotiation process as well as their final approval; these are detailed in Articles 66 and 67 of the constitution.

In case of vacancy of either co-prince, Andorra "recognizes the validity of the interim procedures foreseen by their respective statuses, in order for the normal function of Andorran institutions not to be interrupted".