A duchy is a territory or domain ruled by a duke or duchess. Historically, some duchies in Continental Europe were sovereign, while others (especially in France and Britain) were subordinate districts of a kingdom.
Traditionally, a grand duchy, such as Luxembourg, was generally independent and sovereign. Sovereign duchies were common in the Holy Roman Empire and German-speaking areas. In France, a number of duchies existed in the medieval period. Queen Elizabeth II of the United Kingdom still holds the medieval French title of Duke of Normandy; the only lands still attached to the Duchy of Normandy are the Channel Islands.
In medieval England, the territories of Lancashire and Cornwall were made duchies, with certain powers given to their Dukes.
Today, duchies aren't very common in Europe, primarily because a lot of former monarchies such as France and Russia had their revolutions. However, duchies will always be remembered - in our history textbooks.
- The Duchy of Cornwall - On the Prince of Wales' official web-site
- Tyr Gwyr Gweryn Archived 2015-02-05 at the Wayback Machine The Duchy charters, Cornish foreshore case and much more in full