The French Navy white ensign started to be used between 1636 and 1643, although it was officially issued only from 1661 by an order of Louis XIV that incidentally also prohibited merchant vessels to fly it –an order that was much abused however. It remained in use until 1790, and again from 1814 to 1830.
Sources: Anonymous manuscript from 1670, reprinted in Amsterdam 1966 as «Flags of the World 1669-1670» | Gustave Desjardins, «Recherches sur les drapeaux français», Paris 1874
Sizes: ensign W12 x L18 mm, mast flags W8 x L12 mm, jack W6 x L9 mm, pennant W4 x L48 mm.