Fort-Louis (German Fortlouis [1]) is a French commune with 300 inhabitants (as of 1 January 2015) in the department of Bas-Rhin in the Grand Est region (until 2015 Alsace). It is located on the Rhine, near the German communities Rheinmuenster-Söllingen and Hügelsheim.
In 1686, King Louis XIV of France ordered the construction of a fortress in lower Alsace, immediately on the border with the Margraviate of Baden. It was built in 1687 within ten years on an island of the then unregulated Rhine to plans by Sébastien Le Prestre de Vauban and the fortress engineer Jacques Tarade. The medieval Palatinate in about twenty kilometers away Haguenau was razed to the ground and used the useful stones for the construction of the new fortress on the Rhine.
Two offshore forts were built as bridgeheads on the opposite banks of the Rhine, Alsace on the Alsatian side and the Fort Marquisat on the banks of the Baden. South of the main fort called Fort Carré was built on the island at the same time the regular road grid of the community Fort-Louis, whose settlement promoted the king with privileges. The Fort Marquisat had to be abandoned after the peace of Rijswijk 1697 in the meantime, finally after the Rastatt peace of 1714. The main fortress was stormed in 1793 in the First Coalition War and further destroyed in 1815-18.
Since the rectification of the Rhine in the 19th century, the fort and the village are located on the left bank of the Rhine. Remains of the fortress are still present today.