How do you say in french are my reason for living?

There isn't a direct, literal translation for "are my reason for living" in French that captures the same emotional weight. Here are a few options, depending on the context and the nuance you want to convey:

Formal:

* "Vous êtes la raison de mon existence." (You are the reason for my existence.) This is very formal and strong.

* "Vous êtes ce qui donne un sens à ma vie." (You are what gives meaning to my life.) This is also quite formal.

Informal:

* "Vous êtes tout pour moi." (You are everything to me.) This is very common and conveys strong affection.

* "Vous êtes ma raison de vivre." (You are my reason to live.) This is more direct and conveys a strong emotional dependence.

* "Sans vous, je ne serais rien." (Without you, I would be nothing.) This is less common but emphasizes the person's importance in your life.

More poetic:

* "Vous êtes le soleil qui éclaire ma vie." (You are the sun that illuminates my life.)

* "Vous êtes l'air que je respire." (You are the air I breathe.)

The best option will depend on the specific context and the relationship you have with the person you are speaking to.