any of diverse officials found in numerous countries of medieval and early modern Europe. Originally the term was applied to the chamberlains and troops guarding the palace of the Roman emperor. In Constantine's time (early 4th century), the designation was also used for the senior field force of the army that might accompany the emperor on his campaigns.

During the early European Middle Ages the term palatine applied to various officials among the Germanic peoples. The most important of these was the count palatine, who in Merovingian and Carolingian times (5th through 10th century) was an official of the sovereign's household, in particular of his court of law. The count palatine was the official representative at court proceedings such as oath takings or judicial sentences and was in charge of the records of such proceedings. At first he examined cases in the king's court and was authorized to carry out the decisions; later he had his own court in which he was allowed certain discretion in making decisions. In addition to his judicial responsibilities, the count palatine had administrative functions dealing with the king's household.

Under the German kings of the Saxon and Salian dynasties (919–1125), the function of the counts palatine corresponded to those of the Carolingian missi dominici (missus dominicus), who were representatives of the king in the provinces, responsible for the administration of the royal domain and for the disposition of justice in certain duchies, such as Saxony and Bavaria, and, in particular, Lotharingia (Lorraine). When other palatine rights were absorbed by ducal dynasties, local families, or, in Italy, by bishops, with little of the authority retained, the count palatine of Lotharingia, whose office had been attached to the royal palace at Aachen from the 10th century onward, became the real successor to the Carolingian count palatine. From his office grew the Countship Palatine of the Rhine, or simply the Palatinate, which, from the time of the emperor Frederick I Barbarossa (d. 1190), became a great territorial power. The term palatine recurs in the 14th century, when the emperor Charles IV instituted a court body of household counts palatine, but they had only voluntary jurisdiction and some honorific functions.

In England the term palatinate, or county palatine, was applied in the Middle Ages to counties the lords of which, whether lay or ecclesiastical, exercised powers normally reserved to the crown. Likewise, there were palatine provinces among the English colonies in North America: Cecilius Calvert, Lord Baltimore, was granted palatine rights in Maryland in 1632, as were the proprietors of the Carolinas in 1663.

The word palatinus and its derivatives also translate the titles of certain great functionaries in eastern Europe, such as the Polish wojewoda, a military governor of a province.