A duchy is a medieval country, territory, fief, or domain ruled by a duke or duchess, a high-ranking nobleman hierarchically second to the king or queen in European tradition. The term is used almost exclusively in Europe, where in the present day there is no sovereign duchy (i.e. with the status of a nation state) left.
The term "duke" (like the corresponding "duchy") should not be confused with the title Grand Duke (or Grand Duchy, such as the present-day Grand Duchy of Luxembourg), as there exists a significant difference of rank between the two.
In common European cultural heritage, a grand duke is the third highest monarchic rank, after emperor and king. Its synonym in many Slavic and Baltic European languages (Russian, Lithuanian, etc.) is translated as Grand Prince, whereas most Germanic and Romance European languages (English, French, Spanish, Italian etc.) use expressions corresponding to Grand Duke. Unlike a duke, the sovereign grand duke is considered royalty (or in German, 'royal nobility', Königsadel). The proper form of address for a grand duke is His Royal Highness (HRH), whereas for a non-royal duke in the United Kingdom it is His Grace.
In contrast to this, the rank of a duke differs from one country to the next. In Germany, for example, a duke is listed in the aristocratic hierarchy below an emperor (Kaiser), king (König), grand duke (Großherzog), and elector (Kurfürst) - in that order - whereas in Britain the duke comes third after king/queen and prince (there are no British grand dukes or electors).
In all countries, there existed an important difference between "sovereign dukes" and dukes subordinate to a king or emperor. Some historic duchies were sovereign in areas that would become part of nation-states only during the modern era, such as Germany (a federal empire) and Italy (a unified kingdom). In contrast, others were subordinate districts of those kingdoms that had unified either partially or completely during the medieval era, such as France, Spain, Sicily, Naples, and the Papal States. In England, the term is used in respect of non-territorial entities.
Traditionally, a grand duchy, such as Luxembourg or Tuscany (1569-1860), was generally independent and sovereign. There were also many sovereign or semi-sovereign duchies in the de facto confederate Holy Roman Empire (961-1806) and German-speaking areas.
The medieval German stem duchies (German: Stammesherzogtum, literally "tribal duchy", the official title of its ruler being Herzog or "duke") were associated with the Frankish Kingdom and corresponded with the areas of settlement of the major Germanic tribes. They formed the nuclei of the major feudal states that comprised the early era of the Holy Roman Empire of the German nation (961-1806; in German: Heiliges Römisches Reich Deutscher Nation). These were Schwaben (Swabia, mainly the present-day German state of Baden-Württemberg), Bayern (Bavaria), and Sachsen (Saxony) in pre-Carolingian times, to which Franken (Franconia, at present the northern part of the German state of Bavaria) and Lothringen (Lorraine, nowadays mostly part of France) were added in post-Carolingian times. As mentioned above, such a duke was styled Herzog (literally "the one who is leading [the troops]").
In medieval England, duchies associated with the territories of Lancashire and Cornwall were created, with certain powers and estates of land accruing to their dukes. The Duchy of Lancaster was created in 1351 but became merged with the Crown when, in 1399, Henry Bolingbroke, Duke of Lancaster, ascended the throne of England as Henry IV. Nowadays the Duchy of Lancaster always belongs to the sovereign and its revenue is the Privy Purse. The Duchy of Cornwall was created in 1337 and held successively by the Dukes of Cornwall, who were also heirs to the throne. Nowadays, the Duchy of Cornwall belongs to the sovereign's heir apparent, if there is one: it reverts to the Crown in the absence of an heir apparent, and is automatically conferred to the heir apparent upon birth. These duchies today have mostly lost any non-ceremonial political role, but generate their holders' private income. During the Wars of the Roses, the Duke of York made a successful entry into the City of York, by merely claiming no harm and that it was his right to possess "his duchy of York". Any and all feudal duchies that made up the patchwork of England have since been absorbed within the Royal Family. Other than Cornwall and Lancaster, British royal dukedoms are titular and do not include land holdings. Non-royal dukedoms are associated with ducal property, but this is meant as the duke's private property, with no other feudal privileges attached.
In more recent times, territorial duchies have become rare; most dukedoms conferred in the last few centuries have been of a purely ceremonial or honorific character (see Duke). At present all independent (i.e., sovereign) duchies have disappeared.
Luxembourg, an independent and sovereign nation with a history dating back as far as the 8th century, is the only remaining independent grand duchy, with the Grand Duke Henri (dynasty of Luxembourg-Nassau) as its head of state since the year 2000.
In the Middle East the concept of beylik can be seen as equivalent to duchy ("bey" being a Turkish title for the head of a house, and similar to "duke" when that person is the highest representative of the state in a principality). For example, the Ottoman Empire, first just the nomadic Kay? tribe among the Ghuzz (Oghuz Turks), settled in Bithynia on the border to the Byzantine Empire, evolved under the Sultanate of Rûm (Seljuks in Anatolia) into a border principality (Uç beyli?i /margraviate). It became an independent principality after the Anatolian Seljuk state was shattered by the Mongols. Later it grew further into its own empire by conquering the nearby Anatolian beyliks, also remnants of the Sultanate of Rûm.
The following duchies were part of the medieval Kingdom of Italy (not to be confused with the modern Kingdom of Italy (1860-1945)), which itself was part of the Holy Roman Empire: