Ponthion is a commune in the Marne department in north-eastern France.
It is located southeast of Châlons-en-Champagne.
It was a royal pfalz (crown estate) under both the Merovingian (mainly Neustrian branch) and the Carolingian dynasties. In appears repeatedly in the Frankish royal and ecclesiastical history.
In 753 Pope Stephen II left Rome. Aistulf, when the pope met him at Pavia, refused to enter into negotiations or to hear of a restoration of his conquests. Only with difficulty did Stephen finally prevail upon the Lombard king not to hinder him in his journey to the Frankish kingdom.
The pope thereupon crossed the Great St. Bernard into the Frankish kingdom. the King Pepin the Short received his guest for a conference with at Ponthion in January 754. Stephen implored his assistance against his oppressor the Lombard King Aistulf, and begged Pepin for the same protection for the prerogatives of St. Peter which the Byzantine exarchs had extended to them. The king there promised him orally to do all in his power to recover the Exarchate of Ravenna and the other districts seized by Aistulf, and in the charter establishing the States of the Church, soon after given at Quiercy, promised to restore these prerogatives. The Frankish king received the title of the former representative of the Byzantine Empire in Italy, i.e. "Patricius", and was also assigned the duty of protecting the privileges of the Holy See.