The French 12th Army Corps () was an army corps of the French Army created in 1870. It saw significant action in the Franco-Prussian War, the First World War, and the Second World War.
Commanded by Général Lebrun in the Franco-Prussian War then by General Galliffet from 1882 to 1886.
On the outbreak of the First World War in August 1914, the corps was subordinated to the Fourth Army. It later served on the Italian front under General Jean César Graziani in 1918.
During the Battle of France in 1940, the 12th Army Corps was a cornerstone of the Fifth Army within the Army Group 2. Upon mobilization, the 12th Corps was classified as a Série A formation, indicating it was a high-readiness unit with a substantial core of active-duty officers and modern equipment.
The corps' structure reflected its dual mission of mobile defense and static fortification support:
The sector was organized into several sub-sectors, each reinforced by fortress infantry and position artillery to defend the Maginot Line's northern flank.