The oldest known surviving written valentine attributed to Charles, Duke of Orléans, dates to 1415.
Charles was a French nobleman captured by the English at the Battle of Agincourt on October 25, 1415. He spent roughly 25 years in captivity, much of it in the Tower of London, where he wrote poetry and love letters to his wife, Bonne of Armagnac.
The famous Valentine is a French rondeau that begins with the sentiment “My very gentle Valentine.” It is usually treated as the earliest surviving Valentine message, although surviving medieval manuscripts do not always provide a precise composition date; 1415 is the conventional date linked to his capture and imprisonment.
A later milestone is found in the Paston Letters: Margery Brews wrote to John Paston in 1477, calling him her “right well-beloved Valentine.” That is among the earliest surviving Valentine letters in English, but it is more than six decades later than Charles’s French poem.