The Rossi Codex is a music manuscript collection of the 14th century. The manuscript is presently divided into two sections, one in the Vatican Library and another, smaller section in the Northern Italian town of Ostiglia. The codex contains 37 secular works including madrigals, cacce and, uniquely among trecento sources, monophonic ballatas. The codex is of great interest for trecento musicologists because for many years it was considered the earliest source of fourteenth-century Italian music. Although other pre-1380 sources of secular, polyphonic, Italian music have now been identified, none are nearly so extensive as the Rossi Codex.

The Vatican Apostolic Library, more commonly known as the Vatican Library or informally as the Vat, is the library of the Holy See, located in Vatican City, and is the city-state's national library. It was formally established in 1475, although it is much older—it is one of the oldest libraries in the world and contains one of the most significant collections of historical texts. It has 75,000 codices from throughout history, as well as 1.1 million printed books, which include some 8,500 incunabula.