Although leaving the marital home (in French: abandon du domicile conjugal) can be held against the spouse who leaves in cases of a divorce, judges will usually take into account the circumstances surrounding a particular situation. Unless in a crisis, it is advisable to inform the partner of the decision to leave rather than just disappearing. If it is in the case of crisis, it can definitely be helpful to inform the local police of your intention to leave and why.
If one of the spouses decides to leave and the partner agrees, each person should sign a document to that effect in order to avoid a subsequent accusation of abandon du domicile conjugale. Be sure to keep your copy in a safe place, along with other essential documents. Here is a link to a sample of such a document in French.
http://droit-finances.commentcamarche.net/faq/35164-quitter-le-domicile-conjugal-modele-de-lettre#exemple-de-lettre (updated in 2021)
Finding a place to stay
For an abuse victim who wishes to leave home but has no family or friends who can assist, finding an alternative place to live can be extremely problematic. Though there are both shelters and associations that help, in general requests are handled by social services. This means that a victim must make an appointment through her local Mairie (town hall) with a social worker (travailleur social) who will create a file for her and discuss options. The waiting lists are very long for apartments, and even the shelters offering temporary lodging for abuse victims have few or no spaces immediately available, especially in major cities. Chances are better for mothers of very young children than for women alone.
An emergency telephone number, 115, has been set up by the Service d’Aide Médicale Urgente — referred to as the SAMU — which deals with non-hospital related medical emergencies. It offers same-day shelter to victims as well as to the homeless, but even that service is often flooded with requests and cannot help. Reservations are not permitted, and generally people are housed in poorly maintained premises where hygiene is questionable. Again, a file with social services is highly recommended if a person wants to solicit help from the 115. Be warned: once they find something for you, you will lose their help irrevocably if you decide to move somewhere else.