Je ne veux rien.
This is a literal translation and is grammatically correct.
Here's a breakdown:
* Je: I
* ne...rien: this is a negative construction meaning "nothing"
* veux: want
Here are some other ways to express this sentiment in French, depending on the context:
* Je n'ai besoin de rien. (I don't need anything.)
* Je n'ai aucun désir. (I have no desire.)
* Je ne désire rien. (I desire nothing.)
* Rien ne m'intéresse. (Nothing interests me.)
* Je suis indifférent. (I am indifferent.)
The best way to choose the right phrase depends on the situation and the specific meaning you want to convey.