Reserve-Korps / XVIII RK) was a corps level command of the German Army in World War I. XVIII 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 Generalleutnant Kuno von Steuben, formerly of the Prussian War Academy.

[2] It was still in existence at the end of the war[3] in the 18th Army, Heeresgruppe Deutscher Kronprinz on the Western Front.

In general, Reserve Corps and Reserve Divisions were weaker than their active counterparts In summary, XVIII Reserve Corps mobilised with 24 infantry battalions, 5 machine gun companies (30 machine guns), 6 cavalry squadrons, 12 field artillery batteries (72 guns) and 3 pioneer companies.

On mobilisation, XVIII Reserve Corps was assigned to the 4th Army forming part of the centre of the forces for the Schlieffen Plan offensive in August 1914.