Saint Valentine or Saint Valentinus
His birth date and birthplace are unknown. Valentine's name does not occur in the earliest list of Roman martyrs, that compiled by the Chronographer of 354.
The feast of St. Valentine was first decreed in 496 by Pope Gelasius I, who included Valentine among those "... whose names are justly reverenced among men, but whose acts are known only to God." As Gelasius implied, nothing is known about the lives of any of these martyrs.
According to the Catholic Encyclopedia, the saint whose feast was celebrated on the day now known as St. Valentine's Day was possibly one of three martyred men named Valentinus who lived in the late third century, during the reign of Emperor Claudius II (died 270):
Various dates are given for their martyrdoms: 269, 270 or 273. As Gelasius implied, nothing is known about the lives of any of these martyrs. The name was a popular one in Late Antiquity, with its connotations of valens, "being strong". Several emperors and a pope bore the name,  not to mention a powerful gnostic teacher of the second century, Valentinius, for a time drawing a threateningly large following.
That the creation of the feast for such dimly conceived figures may have been an attempt to supersede the pagan holiday of Lupercalia that was still being celebrated in fifth-century Rome, on February 15 is apparently a figment of the English eighteenth-century antiquarian Alban Butler, embellished by Francis Douce, as Jack Oruch conclusively demonstrated in 1981. Many of the current legends that characterise Saint Valentine were invented in the fourteenth century in England, notably by Geoffrey Chaucer and his circle, when the feast day of February 14 first became associated with romantic love.