The Inner Mongolian Army, also sometimes called the Mengjiang National Army, referred to the Inner Mongolian military units in service of Imperial Japan and its puppet state of Mengjiang during the Second Sino-Japanese War, particularly those led by Prince Demchugdongrub. It was primarily a force of cavalry units, which mostly consisted of ethnic Mongols, with some Han Chinese infantry formations.

Mengjiang, also known as Mengkiang or the Mongol Border Land, officially the Mengjiang United Autonomous Government, was an autonomous zone in Inner Mongolia, formed in 1939 as a puppet state of the Empire of Japan, then from 1940 being under the nominal sovereignty of the Reorganized National Government of the Republic of China. It consisted of the previously Chinese provinces of Chahar and Suiyuan, corresponding to the central part of modern Inner Mongolia. It has also been called Mongukuo or Mengguguo. The capital was Kalgan, from where it was under the nominal rule of Mongol nobleman Demchugdongrub. The territory returned to Chinese control after the defeat of the Japanese Empire in 1945.