Valentine's Day, also called Saint Valentine's Day or the Feast of Saint Valentine, is celebrated annually on February 14. Originating as a Western Christian feast day honoring one or two early saints named Valentinus, Valentine's Day is recognized as a significant cultural, religious, and commercial celebration of romance and romantic love in many regions around the world.

There are numerous martyrdom stories associated with various Valentines connected to February 14, including a written account of Saint Valentine of Rome's imprisonment for performing weddings for soldiers who were forbidden to marry and for ministering to Christians persecuted under the Roman Empire. According to legend, Saint Valentine restored sight to the blind daughter of his judge, and he wrote her a letter signed "Your Valentine" as a farewell before his execution. The Feast of Saint Valentine was established by Pope Gelasius I in AD 496 to be celebrated on February 14 in honour of the Christian martyr, Saint Valentine of Rome, who died on that date in AD 269.

The day first became associated with romantic love within the circle of Geoffrey Chaucer in the 14th century, when the tradition of courtly love flourished. In 18th-century England, it grew into an occasion in which couples expressed their love for each other by presenting flowers, offering confectionery, and sending greeting cards (known as "valentines"). Valentine's Day symbols that are used today include the heart-shaped outline, doves, and the figure of the winged Cupid. Since the 19th century, handwritten valentines have given way to mass-produced greeting cards. In Europe, Saint Valentine's Keys are given to lovers "as a romantic symbol and an invitation to unlock the giver's heart", as well as to children to ward off epilepsy (called Saint Valentine's Malady).

Although not a public holiday in any country, Saint Valentine's Day is an official feast day in the Anglican Communion and the Lutheran Church. Many parts of the Eastern Orthodox Church also celebrate Saint Valentine's Day on July 6 and July 30, the former date in honor of Roman presbyter Saint Valentine, and the latter date in honor of Hieromartyr Valentine, the Bishop of Interamna (modern Terni).

Numerous early Christian martyrs were named Valentine. The Valentines honored on February 14 are Valentine of Rome (Valentinus presb. m. Romae) and Valentine of Terni (Valentinus ep. Interamnensis m. Romae). Valentine of Rome was a priest in Rome who was martyred in 269 and was added to the calendar of saints by Pope Galesius in 496 and was buried on the Via Flaminia. The relics of Saint Valentine were kept in the Church and Catacombs of San Valentino in Rome, which "remained an important pilgrim site throughout the Middle Ages until the relics of St. Valentine were transferred to the church of Santa Prassede during the pontificate of Nicholas IV". The flower-crowned skull of Saint Valentine is exhibited in the Basilica of Santa Maria in Cosmedin, Rome. Other relics are found at Whitefriar Street Carmelite Church in Dublin, Ireland.

Valentine of Terni became bishop of Interamna and is said to have been martyred during the persecution under Emperor Aurelian in 273. He is buried on the Via Flaminia, but in a different location from Valentine of Rome. His relics are at the Basilica of Saint Valentine in Terni (Basilica di San Valentino). Jack B. Oruch states that "abstracts of the acts of the two saints were in nearly every church and monastery of Europe."The Catholic Encyclopedia also speaks of a third saint named Valentine who was mentioned in early martyrologies under date of February 14. He was martyred in Africa with a number of companions, but nothing more is known about him. Saint Valentine's head was preserved in the abbey of New Minster, Winchester, and venerated.

February 14 is celebrated as St. Valentine's Day in various Christian denominations; it has, for example, the rank of 'commemoration' in the calendar of saints in the Anglican Communion. In addition, the feast day of Saint Valentine is also given in the calendar of saints of the Lutheran Church. However, in the 1969 revision of the Roman Catholic Calendar of Saints, the feast day of Saint Valentine on February 14 was removed from the General Roman Calendar and relegated to particular (local or even national) calendars for the following reason: "Though the memorial of Saint Valentine is ancient, it is left to particular calendars, since, apart from his name, nothing is known of Saint Valentine except that he was buried on the Via Flaminia on February 14."

The feast day is still celebrated in Balzan (Malta) where relics of the saint are claimed to be found, and also throughout the world by Traditionalist Catholics who follow the older, pre-Second Vatican Council calendar.

In the Eastern Orthodox Church, St. Valentine is recognized on July 6, in which Saint Valentine, the Roman presbyter, is honoured; in addition, the Eastern Orthodox Church observes the feast of Hieromartyr Valentine, Bishop of Interamna, on July 30