Silvester I (or Sylvester), pope (January, 314 – December 31, 335), succeeded Miltiades and was followed by Marcus. The accounts of his Papacy preserved in the Liber Pontificalis (7th or 8th century) and in Anastasius are little else than a record of the gifts said to have been conferred on the Roman Church by Constantine the Great.

He was represented at the First Council of Nicaea, and is said to have held a council at Rome to condemn the heresies of Arius and others. The story of his having baptized Constantine is pure fiction, as contemporary evidence shows the emperor to have received this rite near Nicomedia at the hands of Eusebius, bishop of that city. According to the 19th century historian Döllinger, the entire legend of Silvester and Constantine, with all its details of Constantine's leprosy and the proposed bath of blood, cannot have been composed later than the close of the 5th century, while it is certainly alluded to by Gregory of Tours and Bede. The so-called Donation of Constantine was long ago shown to be spurious, but the document is of very considerable antiquity, and in Döllinger's opinion, was forged in Rome between 752 and 777. It was certainly known to Pope Adrian I in 778, and was inserted in the false decretals towards the middle of the next century. Silvester's legendary relationship to Constantine was important in the Middle Ages. Pope Silvester II (999-1003) chose the name Silvester in imitation of Silvester I; Silvester II was a close associate of emperor Otto III.