Alsace–Lorraine

Alsace–Lorraine (German: Elsaß–Lothringen), officially the Imperial Territory of Alsace–Lorraine (German: Reichsland Elsaß–Lothringen), was a territory of the German Empire, located in modern-day France. It was established in 1871 by the German Empire after it had occupied the region during the Franco-Prussian War. The region was officially ceded to the German Empire in the Treaty of Frankfurt. French resentment about the loss of the territory was one of the contributing factors to World War I. Alsace–Lorraine was formally ceded back to France in 1920 as part of the Treaty of Versailles following Germany's defeat in the war, but already annexed in practice at the war's end in 1918.

Geographically, Alsace–Lorraine encompassed most of Alsace and the Moselle department of Lorraine. The Alsatian part lay in the Rhine Valley on the west bank of the Rhine River, east of the Vosges Mountains; the section initially in Lorraine was in the upper Moselle valley to the north of the Vosges. Politically, it was the only subdivision of the German Empire dubbed an "Imperial Territory"; as such, it was under the direct administration of the Imperial German state, rather than a quasi-sovereign constituent of the federal Empire, though it was granted a legislature and limited internal autonomy in 1911.

The territory encompassed almost all of Alsace (93%) and over a quarter of Lorraine (26%), while the rest of these regions remained parts of France. For historical reasons, specific legal dispositions are still applied in the territory in the form of a "local law in Alsace–Moselle". Due to its special legal status since reversion to France, the territory has been referred to administratively as Alsace–Moselle. (Alsatian: 's Elsàss–Mosel; German: Elsaß–Mosel or Elsass–Mosel).

Since 2016, the historical territory has been part of the French administrative region of Grand Est.