By the Grace of God

Originally, it had a literal meaning: the divine will was invoked—notably by Christian monarchs—as legitimation (the only one above every earthly power) for the absolutist authority the monarch wielded. This is also known as the divine right of kings, that is, the endorsement of God for the monarch's reign.

The Christian Roman emperors during the late Dominate came remarkably close to acting out the role of God's voice on earth. The eastern emperors, in particular, centralized all power in their hands, reducing the patriarch of Constantinople to their "(state) minister of the cult" and proclaiming their "universal" authority. Elsewhere during the medieval period, kings faced regular challenges to their authority from nobles, clergy, dynastic rivals and foreign powers. Even where they claimed to rule by God's grace, the political realities often reflected otherwise.

By custom, the phrase "by the Grace of God" is restricted to sovereign rulers; in the feudal logic, a vassal could not use it, because he held his fief not by the grace of God almighty, but by grant of a superior noble, (in)directly from the crown. Yet this did not stop kings to continue using it, even when some of them did homage to the pope (as viceregent of God) or another ruler (sometimes even mutually), on account of some (minor or "external") fief, or even for their actual principality, such as the Kingdom of Bavaria, a state of the Holy Roman Empire.

While the "incantation" of divine Grace became a prestigious style figure that few Christian monarchies could resist, it is not a literal carte-blanche from Heaven, but rather a consecration of the "sacred" mystique of the crown. Some of that survives even in modern constitutional monarchies and finds expression in most even mildly religious republics and dictatorships, where all power has been transferred to elected (party) politicians. In modern, especially recently (re-)founded monarchies, more realistic power reports (often crucially a voice in the succession and the purse strings) do in time find expression, sometimes even in abandoning "By the Grace of God", or rather, especially earlier, in the intercalation of compensatory phrases, such as "and the will of the people", or replacing the genitive "sovereign of X-place" by "sovereign of the X-inhabitants", quite meaningful where linked to the Enlightenment-notion of the "social contract", which means the nominal 'sovereign' is in fact potentially subject to national approval, without which a revolution against him can be legitimate.

The phrase was used in Luxembourg until 2000, when Henri, the current grand duke, decided to drop it. Like the use of the term "subject" for the citizens of a monarchy, "by the Grace of God" is a protocolary form that has survived the emancipation of the electorate from its once absolute rulers, who now rule only in name, but without direct political power. During the 20th century during the dictatorship of Francisco Franco in Spain, Spanish coins bore a legend identifying him as Francisco Franco, por la G. de Dios Caudillo de España ("by the G(race) of God, Leader of Spain").

Parallels exist in other civilizations, e.g. Mandate of Heaven of the Chinese empire, where for centuries the official decrees by the emperors of China invariably began with the phrase 「奉天承運皇帝，詔曰」 which is translated as "The Emperor, by the Grace of Heaven, decrees".

Today, even though most western monarchies are constitutional, with all political power having passed to the people (by referendum or, generally, elections), the traditional phrase "by the grace of God" is still included in the full titles and styles of a number of monarchs. In Europe, monarchs still using the style are those of Denmark, Liechtenstein, the Kingdom of the Netherlands, and the United Kingdom.

In other Commonwealth realms, who share the same monarch with the United Kingdom, the style is used in Antigua and Barbuda, Australia, The Bahamas, Barbados, Belize, Canada, Grenada, Jamaica, New Zealand, Solomon Islands, St. Kitts and Nevis, St Lucia, St. Vincent and the Grenadines, and Tuvalu. Papua New Guinea does not use the style.

The phrase is not used in the monarchies of Belgium, Luxembourg (Jean, abdicated 2000), Monaco, Norway (Haakon VII, died 1957), and Sweden (Gustav VI Adolf, died 1973). In Spain, article 56(2) of the 1978 constitution, states that the title of the King of Spain is simply "King of Spain" (Rey de España) but that he "can use the titles that correspond to the Crown". As a result, the King of Spain may use "by the grace of God", but this is not used on official documents.

In some cases, the formula was combined with a reference to another legitimation, especially such democratic notions as the social contract, e.g.

• Louis-Napoléon Bonaparte was crowned Napoléon III, Emperor of the French By the Grace of God and the Will of the Nation (Par la Grâce de Dieu, et la Volonté Nationale) after a plebiscite organized among the French people.
• Oliver Cromwell was Lord Protector by the Grace of God, and the Republic, denoting that he was chosen by God to rule but he was put there by the people of the 'Commonwealth' (British republic).
• Agustín de Iturbide of Mexico was styled Agustín I, By the Providence of God, Constitutional Emperor of Mexico. Mexico's second Emperor Maximilian used the style "By the Grace of God and Will of the People, Emperor of Mexico."
• By the Grace of God and the Will of the Nation (Per Grazia di Dio e Volontà della Nazione) in Kingdom of Italy, as well as in the Italian Empire where the king was styled By the Grace of God and the Will of the [Italian] Nation King of Italy, King of Albania, Emperor of Ethiopia which though omitted the titularity as King of Cyprus and Jerusalem which had instead styled the House of Savoy previously and alongside with Duke of Savoia, King of Sardinia, Prince of Piedmont
• By the Grace of God and the Will of People in Kingdom of Serbia and Kingdom of Yugoslavia. The same title was used in the Polish–Lithuanian Commonwealth when, starting with king Henryk Walezy and ending with king Stanisław August Poniatowski, the king was chosen by the noblemen in a free election.
• Sovereigns of the Kingdom of Hawai'i were styled "By the Grace of God and under the Constitution of the Hawaiian Islands, King (or Queen)"
• Brazilian emperors used the style "By the Grace of God and Unanimous Acclamation of the Peoples, Constitutional Emperor and Perpetual Defender of Brazil" ("Pela Graça de Deus e Unânime Aclamação dos Povos, Imperador Constitucional e Defensor Perpétuo do Brasil") in the constitutional Empire of Brazil.

• Billah
• Dei Gratia Regina, discussing the use of the phrase on coins
• Mandate of Heaven

• The Behistun inscription.