Clement III (c. 1024–1100), born Guibert of Ravenna, was antipope from 1080 until his death. He was elevated in opposition to Gregory VII during the height of the Investiture Controversy ⓘ and was supported by the emperor Henry IV, Holy Roman Emperor ⓘ.

His long claim to the papacy illustrates the depth of division between imperial and papal authority in the late eleventh century.

Early Career

Guibert was appointed Archbishop of Ravenna in 1072 and initially maintained cordial relations with Gregory VII. However, he soon aligned himself with the imperial party as tensions escalated over lay investiture.

In 1076, Henry IV convened a synod at Worms declaring Gregory deposed. In 1080, a council at Brixen elected Guibert as pope under the name Clement III.

Rival Papacy

With imperial backing, Clement established himself in Rome in 1084, where he crowned Henry IV emperor. Gregory VII fled the city and later died in exile.

Although Clement never secured universal recognition, he maintained control of parts of Rome for extended periods and appointed bishops loyal to the imperial cause. His claim persisted through the pontificates of Gregory VII’s successors, including Urban II and Paschal II.

Death and Legacy

Clement III died in 1100. Even after his death, elements of the imperial faction continued to promote rival claimants.

In later centuries he was formally regarded as an antipope. His career underscores how the Investiture Controversy transformed the papacy from an office vulnerable to imperial control into a focal point of ecclesiastical reform and resistance.