Collectio Avellana is a collection containing 244 letters issued by emperors, imperial magistrates and popes. The earliest item is dated to AD 367, the latest to AD 553. Hence, the compilator worked most probably in the second half of the 6th century. Two hundred documents of the Collectio are not known from any other collection. The editor of the Collectio, Günther noticed that it can be divided into five thematic parts (Gunther 1896: 3-96; Steinacker 1902: 14-15; Blaudeau 2013: 4) :
1) no. 1-40 is an independent collection making use of the records of the prefecture of the city of Rome concerning two episcopal elections;
2) no. 41-50 that are derived from the records of the bishopric in Carthage, and consist of the letters of Innocentius I and Zosimus;
3) no. 51-55, the late letters of Leo I not known from any other source, regarding the exile of Bishop Timothy II of Alexandria;
4) no. 56-104 the group of letters from the pontificates of Simplicius, Gelasius, Symmachus, John, Agapet, and Vigilius;
5) no. 105-243 the letters from the records of Hormisdas.
The modern name of the collection derives from the codex Vaticanus Latinus 4961 copied in the monastery Sancti Crucis in fonte Avellana that was considered the oldest by the brothers Ballerini who edited the Collectio in 1787.