Valentine's Day was originally called Saint Valentine's Day or the Feast of Saint Valentine. The February 14 celebration began as a Western Christian liturgical feast day honoring one or more early saints named Valentinus, and is recognized as a significant cultural and commercial celebration in many regions around the world, although it is not a public holiday in any country.

The problem is that numerous early Christian martyrs were named Valentine. However, the two most likely candidates for the original "Saint Valentine" honored on February 14 are (1) Valentine of Rome and (2) Valentine of Terni (you can check them both out on Wikipedia!). The remains of both of these Valentines are to be found in Rome.

More Info: en.wikipedia.org