Prince or princesse du sang (prince or princess of the blood) was a rank in Ancien Régime France. It consisted of all persons who were lawfully descended from a French king, but who were not the child or grandchild of a king. They were entitled to the Altesse Sérénissime (Serene Highness), and occupied a rank sandwiched between the royal family and the nobility.

This contrasts with the more familiar British system, in which the more distant descendants of a monarch merge with the aristocracy or even with commoners. For example, Lady Helen Taylor is descended from George V and is in line for the British throne, but this gives her no special legal rank (she ranks as a duke's daughter). A French person in her position would however be a princess.
