Valentine's Day, also called Saint Valentine's Day or the Feast of Saint Valentine, is celebrated annually on February 14. It originated as a Christian feast day honoring a martyr named Valentine and through later folk traditions, it has also become a significant cultural, religious and commercial celebration of romance and love in many regions of the world.

There are a number of martyrdom stories associated with various Saint Valentines connected to February 14, including an account of the imprisonment of Saint Valentine of Rome for ministering to Christians persecuted under the Roman Empire in the third century. According to an early tradition, Saint Valentine restored sight to the blind daughter of his jailer. Numerous later additions to the legend have better related it to the theme of love: tradition maintains that Saint Valentine performed weddings for Christian soldiers who were forbidden to marry by the Roman emperor; an 18th-century embellishment to the legend claims he wrote the jailer's daughter a letter signed "Your Valentine" as a farewell before his execution;

The 8th-century Gelasian Sacramentary recorded the celebration of the Feast of Saint Valentine on February 14. The day became associated with romantic love in the 14th and 15th centuries when notions of courtly love flourished, apparently by association with the "lovebirds" of early spring. In 18th-century England, it grew into an occasion for couples to express 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. In the 19th century, handmade cards gave way to mass-produced greetings. In Italy, 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).

Saint Valentine's Day is not a public holiday in any country, although it 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 in honor of Roman presbyter Saint Valentine, and on July 30 in honor of Hieromartyr Valentine, the Bishop of Interamna (modern Terni).