Latin: Donatio Constantini
In many manuscripts, the document bears the title “Constitutum domni Constantini Imperatoris” (Ordinance of Lord Constantine Emperor). It is divided into two parts. The first, entitled the “Confessio,” sets forth how the emperor was instructed in the faith by Pope Saint Sylvester I, baptized by him, and cured of leprosy. In the second part, entitled “Donatio,” the emperor is made to recognize the primacy of the Church, and to grant to the Bishop of Rome certain marks and insignia of honor, e.g., the tiara and the imperial robes. In addition the emperor transfers to the pope and his successors, as their property, the city of Rome, Italy as well as the castles, towns, and provinces of all Italy and the West.
The account of the baptism, cure, and donation are entirely legendary, the last being built up, no doubt, on the contributions of Constantine to the Patrimony of Saint Peter. The origin of this document is much disputed. It was composed by an unknown author, between 750 and 850, most probably in France, although many hold in Rome. It is sometimes attributed to the author of the False Decretals (but without sufficient reason), sometimes to some Roman ecclesiastic. Laurentius Valla proved it to be a forgery, 1440. Various opinions exist as to the purpose of the document. Some hold it was intended to support the claims of the popes to secular power in Italy; others, to exalt the power of the popes over the emperors. Most probably it was composed to establish the legitimacy of the foundation of the Western Roman Empire against the emperors of Constantinople.
At any rate the popes never considered this “Donation” as the basis of their power, but placed upon entirely different grounds the foundation of the papal prerogatives and the powers exercised by the Holy See.