Yes, in exceptional cases, posthumous marriage may be authorized by the President of the Republic under article 171 of the French Civil Code.
Two conditions must be met:
- it must be proven that the deceased really wished to marry, based on a sufficient number of facts (his or her behavior, the steps he or she took: the publication of pews is a good indication).
- there must also be serious grounds for celebrating the marriage (a child has been born or is yet to be born, etc.).