Adalbert I of Mainz

Adalbert I von Saarbrücken was Archbishop-Elector of Mainz from 1111 until his death. He played a key role in opposing Henry V, Holy Roman Emperor, during the Investiture Controversy, and secured the election of Lothair III rather than Henry V's chosen heir in 1125, causing later Holy Roman Emperors to make concessions in order to maintain hereditary monarchy.