in french

Of course, mon ami, unless you speak of the RPG (jeu de rôle), then I'm afraid not.

The editor "J'ai lu" have most novels in their collection titled "S-F". A quick search on brought several results, except that some are out of print.

Bonne chance !
The old GURPS Conan book was also translated to french (but good luck finding a copy!)
Bonjour amis d'Hyboria !
Howard's books were published in the 70's in "TSF" collection (Titres SF) then reprinted regularly by "J'ai Lu" with Sprague de Camp and Carter stuff, and a Maddox and a Jordan (I should check this). Also published in the 90's were the Jordan, Maddow and others published by "Fleuve noir", you can still find a lot of them in used books shops !
Que crom guide ta lame, mon ami.