Reserve-Korps / III RK) was a corps level command of the German Army in World War I. III Reserve Corps was formed on the outbreak of the war in August 1914[1] as part of the mobilisation of the Army.

It was initially commanded by General der Infanterie Hans von Beseler, recalled from retirement.

In general, Reserve Corps and Reserve Divisions were weaker than their active counterparts In summary, III Reserve Corps mobilised with 25 infantry battalions, 7 machine gun companies (42 machine guns), 6 cavalry squadrons, 12 field artillery batteries (72 guns) and 3 pioneer companies.

On mobilisation, III Reserve Corps was assigned to the 1st Army on the right wing of the forces that invaded France and Belgium as part of the Schlieffen Plan offensive in August 1914.

With the conclusion of the siege on 10 October 1914, it was assigned to 4th Army and took part in the First Battle of Ypres.