Majesty is an English word derived ultimately from the Latin maiestas, meaning greatness, and used as a style by many monarchs, usually kings or emperors. Where used, the style outranks [Royal] Highness. It has cognates in many other languages, especially Indo-European languages of Europe.
Originally, during the Roman republic, the word maiestas was the legal term for the supreme status and dignity of the state, to be respected above everything else. This was crucially defined by the existence of a specific crime, called laesa maiestas, literally "Violated Majesty" (in English law Lese majesty, via the French Lèse-majesté), consisting of the violation of this supreme status. Various acts such as celebrating a party on a day of public mourning, contempt of the various rites of the state and disloyalty in word or act were punished as crimes against the majesty of the republic. However, later, under the Empire, it came to mean an offence against the dignity of the Emperor.
The term was first assumed by Charles V, who believed that—following his election as Holy Roman Emperor in 1519—he deserved a style greater than Highness, which preceding emperors and kings had used. Soon, Francis I of France and Henry VIII of England followed his example.
After the fall of the Holy Roman Empire, Majesty was used to describe a monarch of the very highest rank— it was generally applied to God. Variations, such as "Catholic Majesty" (Spain) or "Britannic Majesty" (United Kingdom) are often used in diplomatic settings where there otherwise may be ambiguity (see a list).