Early life and career
He was born Ioannis Liapis (Greek: Ιωάννης Λιάπης, Iōánnēs Liápēs) in Oinofyta, Boeotia. He is an Arvanite Greek.
Ieronymos holds degrees in archaeology, Byzantine studies, and theology from the University of Athens. He has undertaken postgraduate studies at the University of Graz, the University of Regensburg and the University of Munich. Following a stint as lector in Christian archaeology at the Athens Archaeological Society under professor Anastasios Orlandos, he taught as a philologist in Lycée Léonin and he was ordained deacon and then presbyter in the Orthodox Church in 1967.
Ieronymos served as Protosyncellus of the Metropolis of Thebes and Livadeia, abbot of the monasteries of the Transfiguration of Sagmata and Hosios Loukas, and Secretary, later Archsecretary, of the Holy Synod of the Church of Greece. In 1981 he was elected Metropolitan Bishop of Thebes and Levadeia. In addition to his pastoral ministry, Ieronymos has been pursuing his work on Christian archaeology and has published two major textbooks: "Medieval Monuments of Euboea" (1970), and "Christian Boeotia" (2006). In 1998, he unsuccessfully contested the election to the throne of the archbishopric of Athens.
On 7 February 2008, Ieronymos was elected the new Archbishop of Athens and All Greece by the Holy Synod of the Church of Greece, receiving 45 out of 74 votes in a two-ballot process. He formally took office on 16 February 2008.
As of 2016, Ieronymos, is involved in a dispute with Patriarch Bartholomew I of Constantinople over who has ecclesiastical authority over certain parts of Greece.
On 16 April 2016 he visited, together with Pope Francis and Bartholomew I of Constantinople, the Mòria camp in the island of Lesbos, to call the attention of the world to the refugee issue.