The name Valentinus does not occur in the earliest list of Roman martyrs, compiled by the Chronographer of 354.
The feast of St. Valentine was first established 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 was known, even then, about the lives of any of these martyrs.
The Saint Valentine that appears in various martyrologies in connection with Feb 14 is described either as:
A priest in Rome,
A bishop of Interamna (modern Terni), or
A martyr in the Roman province of Africa.
The first representation of Saint Valentine appeared in the Nuremberg Chronicle (1493); alongside the woodcut portrait of Valentine, the text states that he was a Roman priest martyred during the reign of Claudius II, known as Claudius Gothicus.
He was arrested and imprisoned upon being caught marrying Christian couples and otherwise aiding Christians who were at the time being persecuted by Claudius in Rome. Helping Christians at this time was considered a crime.
Claudius took a liking to this prisoner – until Valentinus tried to convert the Emperor – whereupon this priest was condemned to death.
He was beaten with clubs and stoned; when that failed to kill him, he was beheaded outside the Flaminian Gate. Various dates are given for the martyrdom or martyrdoms: 269, 270, or 273.
The official Roman Martyrology for February 14 mentions only one Saint Valentine.
English eighteenth-century antiquarians Alban Butler and Francis Douce, noting the obscurity of Saint Valentine's identity, suggested that Valentine's Day was created as an attempt to supersede the pagan holiday of Lupercalia.
This idea has lately been contested by Professor Jack Oruch of the University of Kansas.
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.