Reserve-Korps / IX RK) was a corps level command of the German Army in World War I. IX 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 Max von Boehn, brought out of retirement.

[2] It was still in existence at the end of the war[3] in the 5th Army, Heeresgruppe Gallwitz on the Western Front.

17th Reserve Division was slightly stronger than the norm as it included an active infantry brigade.

On mobilisation, IX Reserve Corps was assigned to the North Army, which was held back in Schleswig to defend the German North Sea Coast in case of British landings.