Otgar (died 21 April 847), also spelled Odgar or Otger, was the

archbishop of Mainz The Elector of Mainz was one of the seven Prince-electors of the Holy Roman Empire. As both the Archbishop of Mainz and the ruling prince of the Electorate of Mainz, the Elector of Mainz held a powerful position during the Middle Ages. The Archb ...

from 826 until his death. During the years 838–839, Otgar supported

Louis the Pious Louis the Pious (german: Ludwig der Fromme; french: Louis le Pieux; 16 April 778 – 20 June 840), also called the Fair, and the Debonaire, was King of the Franks and co-emperor with his father, Charlemagne, from 813. He was also King of Aqui ...

against his son

Louis the German Louis the German (c. 806/810 – 28 August 876), also known as Louis II of Germany and Louis II of East Francia, was the first king of East Francia, and ruled from 843 to 876 AD. Grandson of emperor Charlemagne and the third son of Louis the P ...

who was in rebellion and trying to get all of

East Francia East Francia (Medieval Latin: ) or the Kingdom of the East Franks () was a successor state of Charlemagne's Carolingian Empire, empire ruled by the Carolingian dynasty until 911. It was created through the Treaty of Verdun (843) which divided t ...

under his control. He remained strongly opposed to the younger Louis even after the elder's death in 840. He supported

Lothair I Lothair I or Lothar I (Dutch and Medieval Latin: ''Lotharius''; German: ''Lothar''; French: ''Lothaire''; Italian: ''Lotario'') (795 – 29 September 855) was emperor (817–855, co-ruling with his father until 840), and the governor of Bavar ...

in the civil war that lasted until 843. In 842, he even tried to prevent Louis the German from meeting

Charles the Bald Charles the Bald (french: Charles le Chauve; 13 June 823 – 6 October 877), also known as Charles II, was a 9th-century king of West Francia (843–877), king of Italy (875–877) and emperor of the Carolingian Empire (875–877). After a ser ...

and allying with him against Lothair. When Otgar finally died, Louis's hold on East Francia strengthened under his successor,

Rabanus Maurus Rabanus Maurus Magnentius ( 780 – 4 February 856), also known as Hrabanus or Rhabanus, was a Frankish Benedictine monk, theologian, poet, encyclopedist and military writer who became archbishop of Mainz in East Francia. He was the author of the ...

Sources

Annales Fuldenses The ''Annales Fuldenses'' or ''Annals of Fulda'' are East Frankish chronicles that cover independently the period from the last years of Louis the Pious (died 840) to shortly after the end of effective Carolingian rule in East Francia with the ac ...

(Manchester Medieval series, Ninth-Century Histories, Volume II.)

Reuter, Timothy Timothy Alan Reuter (25 January 1947 – 14 October 2002), grandson of the former mayor of Berlin Ernst Reuter, was a German-British historian who specialized in the study of medieval Germany, particularly the social, military and ecclesiastical i ...

(trans.) Manchester: Manchester University Press, 1992.
Archbishops of Mainz 9th-century archbishops 847 deaths Bishops in the Carolingian Empire Year of birth unknown {{RC-archbishop-stub