Donation of Constantine is the most famous and the most important forgery of the Middle Ages. The controversial text of the Donation was used by the papacy for over thousand of years to strengthen its position and power. According to the Vatican, before he died, Constantine made his will that the Roman Church was above all Eastern churches and authorized it with a document. It claims that Donation of Constantine to have been written in the VIIIth century. In January 754 Pope Stephen II went to Paris to seek assistance from King Pepin III to stop the attacks of Lombards. As a result of the agreement reached, in 756 Pepin gave a document providing a legal basis for the establishment of the Papal States, which extended the Pope's temporal sovereignty beyond the Duchy of Rome. This is the first time that the famous forgery came into existence in Rome.Constantine stated in this will that he was supposed to have resigned his crown and the empire into the hands of Pope Sylvester as compensation for having been cured of leprosy by the Pope. In other words, Constantine donated all his political power in the West to the popes. Thanks to the forged will, the papal authority gained a position above all states to be established on Western Roman territory. The Donation became a powerful weapon in the hand of medieval papacy and the basis of papal ideology.The Donation of Constantine was first questioned in the XIth century. Finally, Lorenzo Valla carried out a textual criticism and linguistic analysis of the document and prepared a report that proved indisputably that it was a forgery. This report was to be presented to the ecclesiastical council that held in Florence in 1440. However, Valla's scientific report was hidden from the council and published long after his death.The main purpose of the study is to investigate the Donation of Constantin as a historical document and make some discussion on it.