Infanterie-Division) was a formation of the Imperial German Army in World War I.
The division was disbanded in 1919, during the demobilization of the German Army after World War I.
The 121st Infantry Division initially fought on the Western Front in World War I, entering the line in the Woëvre region at the beginning of May 1915.
It briefly fought in the Battle of the Somme until July 18 when it was transferred to the Eastern Front, where it went into the line on the Styr River until the end of the year.
Cavalry was reduced, artillery and signals commands were formed, and combat engineer support was expanded to a full pioneer battalion.