How do you say in french your my one and only?

There are several ways to say "you're my one and only" in French, depending on the level of formality and sentiment you want to convey. Here are a few options:

Formal:

* Tu es mon unique amour. (You are my only love.)

* Tu es la seule personne que j'aime. (You are the only person I love.)

Informal:

* Tu es mon unique et précieux amour. (You are my unique and precious love.)

* Tu es ma seule et unique. (You are my one and only.)

* T'es tout pour moi. (You're everything to me.)

* Tu es tout ce que j'ai toujours voulu. (You're everything I've ever wanted.)

* Je t'aime plus que tout. (I love you more than anything.)

Romantic/Poetic:

* Tu es mon soleil et ma lune. (You are my sun and my moon.)

* Tu es l'air que je respire. (You are the air I breathe.)

* Je t'aimerai jusqu'à la fin des temps. (I will love you until the end of time.)

The best phrase for you will depend on the context and your relationship with the person you are speaking to.