"The Joy of Yes Forever" read a Vatican note announcing the unusual initiative, which was decorated with silhouettes of a man and a woman embracing and a white cross with pink borders against a blue sky backdrop.
"Engaged couples who have already attended or are presently attending marriage preparation courses are invited to a meeting with the Holy Father," the statement said in several languages.
The Vatican's Pontifical Council for the Family is organising the audience, and participants are invited to register by January 30 to get a spot.
Saint Valentine is believed to have been a priest from the third century AD who was martyred because he secretly married couples in the Christian faith.
February 14 was the date of his martyrdom in 273 AD.