Pope John XVIII

Pope John XVIII (Latin: Ioannes XVIII; died June or July 1009) was the bishop of Rome and nominal ruler of the Papal States from 25 December 1003 to his abdication in July 1009. He wielded little temporal power, ruling during the struggle between John II Crescentius and Emperor Henry II for the control of Rome. He was the last pope to use his baptismal name for centuries. Every pope after him (with the exceptions of Adrian VI and Marcellus II) has taken on a new papal name.

Source: Wikipedia — https://en.wikipedia.org/wiki/Pope_John_XVIII