A steward is an official who is appointed by the legal ruling monarch to represent them in a country, and may have a mandate to govern it in their name; in the latter case, it roughly corresponds with the position of viceroy (for Romance languages), governor, or deputy (the Roman rector, praefectus or vicarius). It was also a term used to refer to the chief servant of a landed estate.
From Old English stíweard, stiȝweard, from stiȝ "hall, household" + weard "wikt:warden, keeper"; corresponding to Dutch: stadhouder, German Statthalter "place holder", a Germanic parallel to French lieutenant.
The Old English term stíweard is attested from the 11th century. Its first element is most probably stiȝ- "house, hall" (attested only in composition; its cognate stiȝu is the ancestor of Modern English sty). Old French estuard and Old Norse stívarðr are adopted from the Old English.
The German and Dutch term (Middle High German stat-halter) is a parallel but independent formation (a calque of lieutenant) corresponding to obsolete English stead holder (stede haldare 1456; also stedys beryng (1460), sted-haldande (1375) steadward, steadsman).
In medieval times, the steward was initially a servant who supervised both the lord's estate and his household. However over the course of the next century, other household posts arose and involved more responsibilities. This meant that in the 13th century, there were commonly two stewards in each house—one who managed the estate and the other, the majordomo, to manage domestic routine. Stewards commonly earned up to 3 to 4 pounds per year. Stewards took care of their lord's castles when they were away. Also, stewards checked on the taxes of the serfs on his lord's manor.
The Lord High Steward of England held a position of power in the 12th to 14th centuries, and the Lord Steward is the first dignitary of the court. The Stewart family traces its appellation to the office of the High Steward of Scotland. Lord High Steward of Ireland is a hereditary office held since the 15th century.
Low Countries 
Stadtholders were appointed by feudal lords to govern parts of their territory. Stadtholders could be appointed for the whole or parts of their territory by the local rulers of the independent provinces in the Low Countries, e.g. the Duke of Gelre appointed a stadtholder to represent him in Groningen. In the Low Countries (which included present-day Netherlands, Belgium and Luxembourg) from the Middle Ages to the 18th century, this was originally an essentially honorary title awarded by the Spanish Habsburg kings to major noblemen in each province. But its nature changed drastically.
Northern Europe 
Danish Statholder 
- In Denmark, a ministerial high office of royal governor in the capital, at Copenhagen Castle
Norwegian Statholder 
In Norway the office of Statholder existed both during the Dano-Norwegian personal union from 1536 to 1814 and during the Swedish-Norwegian personal union from 1814 until it was abolished in 1873. During the latter, the office was also known as Rigsstatholder, i.e. Lieutenant of the Realm. The Statholder governed Norway on behalf of the King. As Norway was a separate kingdom with its own laws and institutions, it was arguably the most influential office in both Denmark-Norway and in the Swedish-Norwegian realm second to that of the king. The office was sometimes held by the Crown Prince, who was styled as Viceroy.
The term Statholder (from German Statthalter) means "place holder", i.e. the one governing on behalf of the king. The modern Norwegian spelling is stattholder.
Southern Europe 
Ban of Croatia 
The Croatian office of the Ban was equivalent of a viceroy. Ban was appointed by the monarch (King of Croats until 1102, King of Hungary 1102–1526, Austrian ruler 1527–1918) with a mandate to govern a part of country, or whole country, in the name of the King of Dalmatia, Croatia and Slavonia.
Ban of Bosnia 
Bosnia was a banate of the Kingdom of Hungary 1136–1377. During that period Bosnia was governed by an autonomus hereditary viceroy, called ban. The last of them, Tvrtko, became the first king of the Kingdom of Bosnia.
Eastern Europe 
The Russian equivalent of "stadtholder" is posadnik; the term sometimes occurs as "stadtholder" in English-language literature. Although there were such legendary posadniks as Gostomysl (9th century), the term first appeared in the Primary Chronicle under the year of 997 to denote the most senior official of an Eastern Slavic town. The earliest posadniks of the city of Novgorod (Holmgard) include a dynasty composed of Dobrynya, his son Konstantin Dobrynich and Ostromir.