1115–1159) was the librarian of the abbey of Montecassino and continuator of the Chronicon monasterii Casinensis, usually called the Monte Cassino Chronicle in English.

According to both Chalandon and Lord Norwich, Peter is a poor historian and writer, much inferior to Leo.

The sovereign was so pleased with him that he appointed him his chaplain and secretary, and would probably have attached him permanently to his person had not Abbot Wibald considered Peter's return necessary to the abbey.

After a long period during which historical sources report nothing about him, his name, Petrus Egidii Tusculanensis, last appears in an act of donation of 1154.

His death had to take place after 1159, the initial deadline for the dating of the codex Casinense 47, in whose obituary on February 26 his name is marked (Petrus diaconus et monacus), the only one, among those of many deacons of the same name commemorated there, which appears written in capital letters.