Valentines’ Day is LA Saint Valentin in French. If you wonder why the article LA when “Saint Valentin” is masculine, the reason is simple: La Saint Valentin is short for La fête de Saint Valentin.
In case you're in the mood for a French Valentine's this year, here are a few helpful terms of endearment, or petits noms, to address to your darling in French.
The masculine chéri/mon chéri and feminine chérie/ma chérie, both mean darling/my darling, and never get out of fashion - well, maybe a little. Other classics are mon coeur (my heart), ma moitié (my half, hopefully the better one), and of course the supreme mon amour (my love,) all working equally well for men and women at any time of the day and night.
If you feel a tad more adventurous, you could try mon lapin (my rabbit), or mon canard (my duck,) or even the ubiquitous mon chou - for that one, you'll want to set aside the fact that it means my cabbage, and you’ll come to find that it’s actually pretty cute. And it technically refers to a chou à la crème anyway, which is a sweet and yummy cream puff.
If you'd like to be more gender specific, and are feeling bold enough, then you could address your male partner with mon roudoudou (a kind of candy), loulou (probably derived from loup/wolf), and mon nounours (my teddy bear.) For women: ma puce (my flea - yes, a French flea is cute!), ma biche (my doe) or ma caille (my quail). When in doubt, you can name pretty much any cute, fuzzy animal.
Take a leap of faith and tack on petit/petite (little) or gros/grosse (big/fat) for even more sparks - BUT be careful how you pair those adjectives...
Petit will most often be used to address a woman: ma petite puce, ma petite caille, mon petit chou. But mon petit loulou, mon petit coeur or mon petit nounours are way too diminutive for an adult man - but they are perfectly fine for a child.
Side note: un (petit) bout de chou, literally a (small) piece of cabbage, is a common synonym for enfant/child.
Along the same cliché lines, un gros roudoudou and un gros canard, for example, will mean big as opposed to fat, and are very acceptable petits noms for your male Valentine. But calling your female Valentine ma grosse caille will be more ambiguous and might not be the greatest idea. First of all, gros can mean either big or fat, depending on the context. Second, few woman would enjoy being called a big quail, or a fat quail, or a big, fat quail, regardless of the context. But who are we to judge, after all?
We also caution against mon gros coeur as it could lead to confusion: avoir le coeur gros means having a heavy heart.
If any or all of the above seems daunting, and you are concerned you might be blanking at the least opportune moment, remember that nothing will ever surpass a good old je t'aime. Succinct and clear, je t'aime is really the only phrase you need to master for a French Valentine’s Day!