Self-styled

A style of office or honorific is an official or legally recognized title. A style, by tradition or law, precedes a reference to a person who holds a post or political office, and is sometimes used to refer to the office itself. An honorific can also be awarded to an individual in a personal capacity. Such styles are particularly associated with monarchies, where they may be used by a wife of an office holder or of a prince of the blood, for the duration of their marriage. They are also almost universally used for presidents in republics and in many countries for members of legislative bodies, higher-ranking judges and senior constitutional office holders. Leading religious figures also have styles.

Traditional forms of address at German-speaking universities:

Traditional forms of address at Dutch-speaking universities:

Traditional forms of address at Italian-speaking universities:

General tradition indicates that monarchs who have ceased to reign but not renounced their hereditary titles, retain the use of their style and title for the duration of their lifetimes, but both die with them. Hence Greece's deposed king is often still styled His Majesty King Constantine II, as a personal title, not as occupant of a constitutional office, since the abolition of the monarchy by the Hellenic Republic in 1974. Similarly, until his death, the last King of Italy, Umberto II, was widely referred to as King Umberto II and sometimes addressed as Your Majesty. In contrast, Simeon of Bulgaria who, subsequent to the loss of his throne in 1947, was elected to and held the premiership of his former realm as "Simeon Sakskoburggotski", and therefore is as often referred to by the latter name as by his former royal title and style.

...
Wikipedia