Reserve-Korps / XXXIX RK) was a corps level command of the German Army in World War I. XXXIX Reserve Corps was formed in December 1914.

The personnel was predominantly made up of kriegsfreiwillige (wartime volunteers) who did not wait to be called up.

[4] On formation in December 1914, XXXIX Reserve Corps consisted of two divisions.

[5] but was weaker than an Active Corps In summary, XXXIX Reserve Corps mobilised with 18 infantry battalions, 2 cavalry detachments, 24 field artillery batteries (96 guns), 2 cyclist companies and 2 pioneer companies.

Generalleutnant von Lauenstein remained as commander of XXXIX Reserve Corps.