FORGED — this document is not what it claims to be, or its attribution is contested. See the summary.
A forged grant in which Constantine, cured of leprosy by pope Sylvester, hands the western empire to the papacy and withdraws to Byzantium so as not to crowd it. It was quoted as genuine for seven hundred years, embedded in the Pseudo-Isidorian collection and in canon law, and demolished in 1440 by Lorenzo Valla on the philology alone — the Latin is of the eighth century and not the fourth. ⚠ It is held here because it shaped what people believed, not because any of it happened.
the single most consequential forgery in western church history; Valla's exposure is itself a founding text of historical criticism
Received it
1054 — Pope Leo IX (Affirms). In his letter of 1054 to Michael Cerularius, Leo IX cites the Donation to show that the Holy See possessed both an earthly and a heavenly imperium, the royal priesthood. New Advent (Fathers and Catholic Encyclopedia) · Catholic Encyclopedia (1909), s.v. 'Donation of Constantine'
c. 1170 — Theodore Balsamon (Affirms). The forgery was known to the Greeks in the second half of the twelfth century, when it appears in the canonical collection of Theodore Balsamon — so the East received it as law as readily as the West. New Advent (Fathers and Catholic Encyclopedia) · Catholic Encyclopedia (1909), s.v. 'Donation of Constantine': 'It was known to the Greeks in the second half of the twelfth century, when it appears in the collection of Theodore Balsamon (1169 sqq.)'
Refused it
1433 — Nicholas of Cusa (Rejects). Cusa called it a dictamen apocryphum — an apocryphal composition — in the third book of his De concordantia catholica. New Advent (Fathers and Catholic Encyclopedia) · Catholic Encyclopedia (1909), s.v. 'Donation of Constantine', citing De Concordantia Catholica III, ii (Basle edition of his Opera, 1565)
1440 — Lorenzo Valla (Rejects). Valla proved the forgery with certainty, and the method — reading the Latin itself for the age it belonged to — did as much for historical criticism as the verdict did for the Donation. New Advent (Fathers and Catholic Encyclopedia) · Catholic Encyclopedia (1909), s.v. 'Donation of Constantine': 'Lorenzo Valla (De falso credita et ementita Constantini donatione declamatio, Mainz, 1518) proved the forgery with certainty'
1588–1607 — Cesare Baronio (Rejects). Rome's own annalist admitted in the Annales Ecclesiastici that the Donation was a forgery. New Advent (Fathers and Catholic Encyclopedia) · Catholic Encyclopedia (1909), s.v. 'Donation of Constantine': 'Baronius in his Annales Ecclesiastici (ad an. 324) admitted that the Donatio was a forgery'