The most popular belief about St Valentine is that he was a priest from Rome in the third century AD.
Emperor Claudius II had banned marriage because he thought married men were bad soldiers. Valentine thought this was unfair, so he broke the rules and arranged marriages in secret.
When Claudius found out, Valentine was sentenced to death and thrown in jail. There, he fell in love with the jailor's blind daughter.
His love and belief in God cured her blindness, and when he was taken to be killed on 14 February he sent her a love letter signed "From your Valentine".