(Königlich Sächsisches) Reserve-Korps / XII RK) was a corps level command of the German Army in World War I. XII 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 Artillerie Hans von Kirchbach, recalled from retirement.

[2] It was still in existence at the end of the war[3] in Armee-Abteilung C, Heeresgruppe Gallwitz on the Western Front.

24th Reserve Division was formed by units drawn from the XIX Corps District.

[10] On mobilisation, XII Reserve Corps was assigned to the predominantly Saxon 3rd Army on the right wing of the forces that invaded France as part of the Schlieffen Plan offensive in August 1914.