Petros Themelis was born in Thessaloniki. He completed his secondary education at the Experimental School of the University of Thessaloniki. He received an undergraduate degree in History and Archeology from the Faculty of Philosophy at the University of Thessaloniki and a PhD from the Archaeological Institute at the University of Munich. He worked as scientific assistant in the Archaeological Service of the District of Thessaloniki and participated in excavations (Stratoni in Chalcidice, at Pella and Vergina). From 1963 to 1980, he served as curator and later as ephor of Antiquities for Elis–Messenia, Attica–Euboea, Phokis–Lokris and Aetolia-Acarnania. For a three-year period (1977-1980), he was director of the Archaeological Museum at Delphi. From 1980 to 1984, he was the head of the Ephorate of Palaeoanthropology and Speleology.

From 1984 to 2003, he taught as a professor of Classical Archeology at the University of Crete, and served as Vice-Chancellor for Academic Affairs and also as President of the Research Committee in the same university. From 1985 to 2003, he headed the university research excavation in Sector I at ancient Eleutherna. From 1986 until the present day, he runs the excavation and restoration project in ancient Messene, for which endeavours he was awarded two Europa Nostra awards — in 2006 in Madrid and in 2011 in Amsterdam.

Publications: Ten monographs, two hundred and fifty scientific studies, book reviews, archaeological guides, excavation reports, introductions to published works, articles in encyclopedias and translations. His serial-columns are regularly published in the daily Athenian and Messenian press.

ΗΟΝOURS: Honorary citizen of Messene, Androusa and Kalamata, a lifetime-member of the Archaeological Society at Athens, corresponding member of the Archaeological Institute of America, member of the Society of Euboean Studies, of the German Archaeological Institute, of the Austrian Archaeological Institute, member of the Committee for the Conservation of the Acropolis Monuments, Chairman of the Society of Messenian Archaeological Studies, and Vice-President of the Centre for the Study of Modern Pottery–G. Psaropoulos Foundation.

In 2005, he was honored with the Commander’s Cross of the Order of the Phoenix by the President of the Hellenic Republic Konstantinos Stephanopoulos, for his teaching, research and excavation works. In 2016, he was appointed, for the same reasons, a Grand Commander of the Order of the Phoenix by the President of the Hellenic Republic Prokopis Pavlopoulos. Also in 2016, he was appointed Honorary Professor of the University of Peloponnese.