In the Low Countries, stadtholder (Dutch: stadhouder, Dutch pronunciation: [ˈstɑtˌɦʌudər]), is an office of steward, designated a medieval official and then a national leader.
The title was used for the official tasked with maintaining peace and provincial order in the early Dutch Republic and, at times, became de facto head of state of the Dutch Republic during the 16th to 18th centuries, which was an effectively hereditary role. For the last half century of its existence, it became an officially hereditary role and thus a monarchy (though maintaining republican pretence) under Prince William IV. His son, Prince William V, was the last stadtholder of the republic, whose own son, King William I, became the first king of the Netherlands. The Dutch Monarchy is only distantly related to the first stadtholder of the young Republic, William of Orange, the leader of the successful Dutch Revolt against the Spanish Empire, his line having died out with William III.
The title stadtholder is roughly comparable to England's historic title Lord Lieutenant.
Stadtholder means "steward". Its component parts literally translate as "place holder," or as a direct cognate, "stead holder" (in modern Dutch "stad" means "city", but the older meaning of "stad" - also "stede" - was "place", and it is a cognate of English "stead", as "in stead of"), it was a term for a "steward" or "lieutenant". Note, however, that is not the word for the military rank of lieutenant, which is luitenant in Dutch.
Stadtholders in the Middle Ages were appointed by feudal lords to represent them in their absence. If a lord had several dominions (or, being a vassal, fiefs), some of these could be ruled by a permanent stadtholder, to whom was delegated the full authority of the lord. A stadtholder was thus more powerful than a governor, who had only limited authority, but the stadtholder was not a vassal himself, having no title to the land. The local rulers of the independent provinces of the Low Countries (which included the present-day Netherlands, Belgium and Luxembourg) made extensive use of stadtholders, e.g. the Duke of Guelders appointed a stadtholder to represent him in Groningen.