Emperor vs King: The Real Differences Between the Two Titles
Emperor vs king compared: where each title comes from, why an emperor was seen as higher, how kings could serve under emperors, which empires used the title, and why only Japan has an emperor today.
Last updated September 2026
Contents10
The emperor vs king question is about more than a grander name. A king rules a kingdom. An emperor, in the old sense, rules an empire.
That means several peoples, lands or even kingdoms under one crown. For centuries European custom ranked emperors above kings. This page compares the two titles and explains where each comes from. It also shows how the difference worked in practice.
TL;DR: A king or queen is the monarch of one kingdom. An emperor claims power over many peoples or several kingdoms. By custom, emperors ranked higher. Kings sometimes served under emperors, as in the German Empire after 1871. The word emperor comes from the Roman imperator. Today only Japan has a reigning emperor.
Emperor vs king at a glance
| Point | King | Emperor |
|---|---|---|
| Rules over | One kingdom, usually one main people | An empire: several peoples, lands or kingdoms |
| Word origin | Old English cyning, related to "kin" | Latin imperator, "commander" |
| Traditional rank | Below an emperor | Highest monarchical rank in European custom |
| Female form | Queen (regnant) | Empress (regnant) |
| Could rule over the other? | No | Yes; some emperors had kings as vassals |
| Reigning today | Many, such as in the UK, Spain and Sweden | One: the Emperor of Japan |
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Where the two titles come from
King comes from Old English cyning, a word related to "kin", suggesting a leader of a people or family group. Other languages have their own equivalents: rex in Latin, roi in French, König in German.
Emperor comes from the Latin imperator. In the Roman Republic, soldiers gave this honour to a winning general. Augustus, Rome's first emperor, used it as part of his name.
Later rulers did the same. From Rome, the idea of an emperor above kings passed to Byzantium and to the Holy Roman Empire in the West. Later it passed to Russia, Austria and Germany. The Russian title tsar comes from the Latin Caesar.
Why an emperor ranked above a king
The idea behind the title was rule over the whole world. The Roman emperor ruled the known Mediterranean world. Medieval emperors claimed to inherit that role. In 800 the Pope crowned Charlemagne emperor. The title then meant the leading Christian ruler of the West, above other kings.
In practice, rank depended on power. The kings of France and England never accepted the Holy Roman Emperor as their superior. For that office, see the Holy Roman emperor page.
Was an emperor always senior?
Precedence of emperors over kings.
Status: Disputed. Custom, not a fixed rule.
Note: By old European custom, emperors came first among monarchs. Writers on heraldry treated emperor as the highest rank. But no treaty or law ever bound all states to that order.
Strong kings rejected imperial claims. In 1815 the Congress of Vienna ranked ambassadors by length of service, not by the rank of the monarchs who sent them. The ranking was a matter of prestige more than law.
Sources: Heraldica, "Emperor"; Britannica, "Emperor" (dictionary).
Kings who served under emperors
Some empires held whole kingdoms. Germany united in 1871, and the King of Prussia became German Emperor. The kings of Bavaria, Saxony and Württemberg kept their crowns. But they sat inside his empire. In the Holy Roman Empire, the King of Bohemia was one of the electors who chose the emperor.
Britain gave its monarch a second, imperial title. Queen Victoria became Empress of India in 1876. She stayed Queen of the United Kingdom as well. The title passed to her heirs. George VI gave it up after India became independent in 1947.
Empires that used the title emperor
| Empire | Title | Ended |
|---|---|---|
| Roman and Byzantine | Imperator; basileus | 476 in the West; 1453 in the East |
| Holy Roman Empire | Emperor | 1806 |
| Russian Empire | Tsar, then emperor (from 1721) | 1917 |
| Chinese empires | Huangdi | 1912 |
| Mughal Empire | Padshah | 1857 |
| French (Napoleon I and Napoleon III) | Empereur | 1815; 1870 |
| Austrian and Austro-Hungarian | Kaiser | 1918 |
| German Empire | Kaiser | 1918 |
| Ethiopian Empire | Negusa Nagast ("king of kings") | 1974 |
| Japan | Tenno | Still reigning |
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The Ethiopian title "king of kings" shows the idea plainly. The emperor stood above other kings. The Persian shahanshah meant the same.
Emperor vs king outside Europe
Other traditions drew the same line with their own words.
- China: early rulers used wang, usually translated "king". In 221 BCE the first Qin emperor united China and created a new title, huangdi, to set himself above the old kings. Emperors used it until 1912.
- Persia: the ruler's title shahanshah means "king of kings", marking rule over lesser kings.
- Ethiopia: the emperor's title, negusa nagast, also means "king of kings".
- Japan: the emperor's title, tenno, is translated "emperor" in English because of the ruler's status and long line, not because Japan ruled other kingdoms.
Rulers who were both
Some monarchs held both titles at once. That shows they were separate offices.
- Charlemagne was King of the Franks from 768 and was crowned emperor in 800.
- Napoleon I was Emperor of the French and also King of Italy from 1805.
- Wilhelm I and his successors were German Emperor and King of Prussia.
- Franz Joseph was Emperor of Austria and King of Hungary from 1867.
- Victoria and her heirs were queen or king of the United Kingdom and, from 1876 to 1947, emperor or empress of India.
Queens and empresses
The female forms follow the same split. A queen regnant rules a kingdom in her own right. An empress regnant rules an empire in her own right. Many more women held the titles as wives of rulers.
- Catherine the Great ruled Russia as empress in her own right from 1762 to 1796.
- Wu Zetian ruled China as emperor in her own right from 690 to 705, the only woman to do so.
- Maria Theresa ruled the Habsburg lands, including Hungary and Bohemia, as queen from 1740. She was Holy Roman Empress only as the wife of Emperor Francis I.
- Victoria was a queen regnant who added the imperial title Empress of India in 1876.
The one emperor today
Emperor Naruhito of Japan came to the throne on 1 May 2019, after his father, Akihito, stepped down. Under Japan's constitution he is "the symbol of the State and of the unity of the people". He has no powers related to government. So the only emperor left has less political power than several reigning kings. The kings of Saudi Arabia and Jordan are two.
The title of emperor began in Rome. Our guide to the best Roman history books includes Mary Beard's book on what emperors actually did.
Verdict: emperor vs king in one sentence
Emperor vs king is a difference of scope and prestige. A king rules one kingdom. An emperor claims rule over many peoples and, by custom, outranks kings.
The ranking was never a fixed law. Today the title survives only in Japan, where the emperor is a symbol without political power. For what makes a state an empire, see empire meaning. For the wider picture, see the monarchy hub.
Sources checked for this page
- Britannica, "Emperor" (dictionary)
- Britannica, "King"
- Heraldica, "Emperor"
- The Imperial Household Agency, "The Emperor"
- Britannica, "Tsar"
- Britannica, "Victoria: Queen, Reign, Legacy"
Questions people also ask
Is an emperor higher than a king?
Traditionally, yes. In European custom an emperor ranked above a king, and some emperors had kings as their subjects. There was never a single binding rule, and powerful kings often refused to accept any emperor's superiority.
Are there any emperors today?
One. Emperor Naruhito of Japan, who came to the throne in 2019, is the only reigning monarch who holds the title emperor.
Where does the word emperor come from?
From the Latin imperator, originally a title for a victorious Roman general, which Augustus and his successors made part of their name.
Was Queen Victoria an empress?
Yes. She took the title Empress of India in 1876 and was proclaimed at Delhi in 1877. British monarchs held the title until George VI gave it up after Indian independence.