The Elector of Trier was one of the Prince-Electors of the Holy Roman Empire and, in his capacity as archbishop, administered the archdiocese of Trier. The territories of the electorate and the archdiocese were not, however, equivalent.
The transient authority of archbishops was not gained without opposition. The German kings Otto IV and Conrad IV in 1308 granted charters to the city of Trier, authorizing the jurisdiction of its archbishop, Baldwin of Luxembourg. This prince, brother of Emperor Henry VII, who ruled from 1307 to 1354, was the real founder of the power of Trier. Although his predecessor, Diether III of Nassau, had left the electorate heavily encumbered with debt, Baldwin raised it to great prosperity with the help of the emperors Henry VII, Louis the Bavarian and Charles IV, to whom he had rendered active political and military support. He enlarged his territory almost to its ultimate extent. He assumed the title of Arch-Chancellor of Gaul and Aries (or Burgundy). In 1315 he accepted the claim of the Archbishop of Cologne, to hold the highest rank among the spiritual princes of the Empire after the Archbishop of Mainz, with the Elector of Trier holding third place in the electoral college. After Baldwin's death the prosperity of Trier was reduced by wars and disputes between rival claimants.
In 1456, the estates united for the purpose of restoring order and secured the right to elect their archbishop. Throughout the Middle Ages, the Sancta Civitas Trevirorum [Latin, “Holy City of Trier”] was a flourishing site of religious foundations and became a great center of monastic learning. In the latter half of the 16th century the supervision of the electorate's educational system was taken over by the Jesuits. The university, founded in 1473, continued in operation until 1797.
Archbishop-Elector Richard von Greiffenklau (1467-1531) successfully opposed the Reformation. One of his acts was the exhibition to the public of the Holy Robe of Trier, which is believed to have been worn by Jesus before His Crucifixion. Trier thereafter became one of the major destinations of Christian pilgrims.