Most Christian Majesty

The precise style of French Sovereigns varied over the years. Currently, there is no French sovereign; three distinct traditions (the Legitimist, the Orleanist, and the Bonapartist) exist, each claiming different forms of title.

The three styles laid claim to by pretenders to the French throne are:

The Latin term Francorum Rex was the official Latin title of the "King of the Franks" after the accession of the Carolingian Dynasty (sometimes taking the form of Rex Francorum); this title was used in official documents until French replaced Latin as the formal language of legal documents, and remained used on coins until the 18th century. However, from as early as the 12th century, the form Franciae Rex ("King of France") was also used.

This title Rex Christianissimus, or Roi Très-chrétien owed its origins to the long, and distinctive, relationship between the Catholic Church and the Franks. France was the first modern state recognised by the Church, and was known as the 'Eldest Daughter of the Church'; Clovis, the King of the Franks, had been recognised by the Papacy as a protector of Rome's interests. Accordingly, this title was frequently accorded to the French Kings (although on a number of occasions Kings of other realms would be addressed as such by the Church), and came into frequent use during the reign of Charles VI; under his son, Charles VII, it became recognised as a hereditary and exclusive title of the Kings of France. Pope Julius II, allied between 1510 and 1513 with Henry VIII of England against Louis XII of France, considered transferring the title from the French monarch to the English monarch, drafting a Papal brief to this effect; however, it was never issued. French kings thus continued to use the title, in particular on diplomatic documents, less frequently in France itself or in everyday parlance.

With the French Revolution came the writing of a Constitution for France. As part of the reforms, the monarch ceased to be an absolute ruler of hereditary lands deriving power from God; instead, he became a constitutional ruler ruling by the will of the French People and for the good of the French People. By a decree on 12 October 1789, the king's title was thus changed from 'By the Grace of God, King of France and Navarre' to 'By the Grace of God and by the constitutional law of the State, King of the French' (French: Par la grâce de Dieu et par la loi constitutionnelle de l'État, Roi des Français), becoming official with the institution of the new constitution on 1 October 1791. The monarchy was abolished a year later, and the Bourbon supporters supported Louis XVI, and then Louis XVII and Louis XVIII, as King of France and Navarre rather than King of the French, under which title the Bourbons were restored in 1815. However, the constitutional monarchy was revived in 1830, with the Bourbon deposition. Although the Orleanist constitutional monarchy, the so-called 'July Monarchy', was abolished in 1848, the heirs of Louis-Philippe continued to claim the title and legacy.

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Wikipedia