His/Her Illustrious Highness (abbreviation

Abbreviation

An abbreviation is a shortened form of a word or phrase. Usually, but not always, it consists of a letter or group of letters taken from the word or phrase...

: H.Ill.H.) is the English-language form for a style used by various members of the European aristocracy

Aristocracy

Aristocracy , is a form of government in which a few elite citizens rule. The term derives from the Greek aristokratia, meaning "rule of the best". In origin in Ancient Greece, it was conceived of as rule by the best qualified citizens, and contrasted with monarchy...

.

It is used to translate the Middle High German

Middle High German

Middle High German , abbreviated MHG , is the term used for the period in the history of the German language between 1050 and 1350. It is preceded by Old High German and followed by Early New High German...

 word Erlaucht , similar to later Durchlaucht

Serene Highness

His/Her Serene Highness is a style used today by the reigning families of Liechtenstein and Monaco. It also preceded the princely titles of members of some German ruling and mediatised dynasties as well as some non-ruling but princely German noble families until 1918...

reserved for the Princes of the Holy Roman Empire

Princes of the Holy Roman Empire

The term Prince of the Holy Roman Empire denoted a secular or ecclesiastical Imperial State, who ruled over an immediate fief directly assigned by the Holy Roman Emperor...

. From the Early modern period

Early modern period

In history, the early modern period of modern history follows the late Middle Ages. Although the chronological limits of the period are open to debate, the timeframe spans the period after the late portion of the Middle Ages through the beginning of the Age of Revolutions...

, the style Erlaucht has been used by the members of those comital

Graf

Graf is a historical German noble title equal in rank to a count or a British earl...

 families (Reichsgrafen), who like the princes held the status of Imperial immediacy. They retained it even after the German Mediatisation

German Mediatisation

The German Mediatisation was the series of mediatisations and secularisations that occurred in Germany between 1795 and 1814, during the latter part of the era of the French Revolution and then the Napoleonic Era....

 of 1802/03, confirmed by the Bundesversammlung

Bundesversammlung (German Confederation)

The Federal Assembly was the only central institution of the German Confederation from 1815 until 1848, and from 1850 until 1866. The Federal Assembly had its seat in the palais Thurn und Taxis in Frankfurt...

 of the German Confederation

German Confederation

The German Confederation was the loose association of Central European states created by the Congress of Vienna in 1815 to coordinate the economies of separate German-speaking countries. It acted as a buffer between the powerful states of Austria and Prussia...

 in 1828. It was also adopted by the cadet members of some princely families like Colloredo-Mansfeld, Fugger

Fugger

The Fugger family was a historically prominent group of European bankers, members of the fifteenth and sixteenth-century mercantile patriciate of Augsburg, international mercantile bankers, and venture capitalists like the Welser and the Höchstetter families. This banking family replaced the de'...

, Khevenhüller

Khevenhüller

Khevenhüller is the name of a Carinthian noble family documented there since 1356 which originally came from the Upper Palatinate in Franconia and which later had their prinicipal seat on Landskron Castle. In the 16th century the family split into the two branches of ...

, Salm

House of Salm

The House of Salm was a noble family originating in the Belgian Ardennes and ruling Salm. It is above all known for the experiences of the branch which came to be located in the Vosges Mountains and over time came to rule over a principality whose capital was Badonviller then Senones.Its notable...

, Schönburg

House of Schönburg

Schönburg is the name of an old noble house, formerly with properties in present day Saxony, Thuringia and Bohemia.- History :...

, Starhemberg

Starhemberg

----Starhemberg is the name of an Austrian noble family hailing from Upper Austria, specifically Steyr and Steinbach, who were Counts of the Empire from 1643, raised to princes in 1765...

, Stolberg

Stolberg-Stolberg

Stolberg-Stolberg was a county of the Holy Roman Empire located in the southern Harz region. Its capital was the town of Stolberg, now in Saxony-Anhalt, Germany....

, Waldburg

House of Waldburg

The House of Waldburg is a princely family of Upper Swabia, founded some time previous to the 12th century; the cadet lineages are comital families....

 or Waldeck-Pyrmont

Waldeck (state)

Waldeck was a sovereign principality in the German Empire and German Confederation and, until 1929, a constituent state of the Weimar Republic. It comprised territories in present-day Hesse and Lower Saxony, ....

. Mediate comital families were entitled to the style Hochgeboren

Hochwohlgeboren

Hochwohlgeboren is a form of address for members of the lower German nobility or landed gentry. The English translation is High Well Born.-German usage:...

.

It is sometimes used to translate the Russian word Ssiatelstvo (Сиятельство), a style used by members of some Russian princely families (also sometimes translated as Serene Highness

Serene Highness

His/Her Serene Highness is a style used today by the reigning families of Liechtenstein and Monaco. It also preceded the princely titles of members of some German ruling and mediatised dynasties as well as some non-ruling but princely German noble families until 1918...

).