An emperor (from the Latin "imperator") is a (male) monarch, usually the sovereign ruler of an empire or another type of imperial realm. Empress is the feminine form. As a title, "empress" may indicate the wife of an emperor (empress consort) or a woman who is a ruling monarch (empress regnant). Emperors are generally recognized to be above kings in honor and rank.

Today the Emperor of Japan is the only remaining emperor on throne in the world.

Distinction from other monarchs

Outside the European context, "emperor" is a translation given to holders of titles who are accorded the same precedence as European emperors in diplomatic terms. In reciprocity, these rulers may accredit equal titles in their native languages to their European peers. Due to centuries of international convention, this has become the dominant rule to identifying an emperor in the modern era.

Also, historians have liberally used "emperor" and "empire" anachronistically and out of its Roman and European context to describe any large state and its ruler in the past and present. "Empire" became identified with vast territorial holdings rather than the title of its ruler by the mid-18th century. Voltaire sardonically described the Holy Roman Empire as "neither Holy, nor Roman, nor an Empire" since by his time it was little more than an informal association of German states and its "Emperor", though ruler of Austria and king of Hungary and Bohemia, had almost no authority within the non-Austrian parts of the territory.

Roman tradition

In the Roman tradition a large variety in the meaning and importance of the imperial form of monarchy developed: in intention it was always the highest office, but it could as well fall down to a redundant title for nobility that had never been near to the "Empire" they were supposed to be reigning. Also the name of the position split in several branches of Western tradition, see below.

Importance and meaning of Coronation ceremonies and regalia also varied within the tradition: for instance Holy Roman Emperors could only be crowned emperor by the pope, which meant the coronation ceremony usually took place in Rome, often several years after these emperors had ascended to the throne (as "king") in their home country. The first Latin Emperors of Constantinople on the other hand had to be present in the newly conquered capital of their Empire, because that was the only place where they could be granted to become Emperor.

Early Roman Emperors avoided any type of ceremony or regalia different from what was already usual for 'republican' offices in the Roman Republic: the most intrusive change had been changing the color of their robe to 'purple'. Later new symbols of worldly and/or spiritual power, like the orb became an essential part of the Imperial accessories.