A king-emperor (feminine queen-empress) is a sovereign ruler who is simultaneously a king of one territory and emperor of another. This title usually results from a merger of a royal and imperial crown (as in Austria-Hungary), but recognises that the two territories are different politically or culturally and in status (an emperor sometimes being considered higher in rank than a king, particularly in the German states). It also denotes a king's imperial status through the acquisition of an Empire or vice versa.
The dual title signifies a sovereign's dual role, but may also be created to improve a ruler's prestige. Both cases, however, show that the merging of rule was not simply a case of annexation where one state is swallowed by another, but rather of unification and almost equal status, though in the case of the British monarchy the suggestion that an emperor is higher in rank than a king was avoided by creating the title king-emperor (queen-empress) instead of emperor-king (empress-queen).
Following the Proclamation of Empire in 1877, when the British Crown took over from the East India Company the administration of British India, Queen Victoria, was considered to have gained Imperial status and assumed the title Empress of India. She was thus the Queen-Empress, and her successors, till George VI, were known as King-Emperors; this title was the shortened form of the full title, and in widespread popular use.
The reigning Queen-Empress used the initials R I (Rex/Regina Imperator/Imperatrix) or the abbreviation Ind. Imp. (Indiae Imperator/Imperatrix) after their name (while the one reigning Queen-Empress, Victoria, used the initials R I, the three consorts of the married King-Emperors simply used R). This was also used on British coins, including coins of George VI dating to 1948, even though the Indian Empire ended in 1947.1867 the multi-national but Austrian-German ruled Austrian Empire, facing growing nationalism, saw a reform that gave nominal and factual rights to Hungarian nobility culminating in the revival of the Austrian-annexed Kingdom of Hungary and therefore creating both the dual-monarchic union state of Austria-Hungary and the dual title of king-emperor (though in German the word order of Kaiser und König follows the rank, as well of the titles as of the received importance of the countries).
Therefore the Habsburg dynasty ruled as Emperors of Austria over the western and northern half of the country and as Kings of Hungary over the Kingdom of Hungary which enjoyed some degree of self-government and representation in joint affairs (principally foreign relations and defence). The federation bore the full name of "The Kingdoms and Lands Represented in the Imperial Council and the Lands of the Crown of St. Stephen".