Military districts are formations of a state's armed forces (often of the Army) which are responsible for a certain area of territory. They are often more responsible for administrative than operational matters, and in countries with conscript forces, often handle parts of the conscription cycle.

Navies have also used a similar model, with organizations such as the United States Naval Districts. A number of navies in South America used naval districts at various points in time.

There were 76 northern military districts or Military Regions (軍區), or War Areas, which were the largest formations of the National Revolutionary Army, under the National Military Council, chaired by Chiang Kai Shek during the Second Sino-Japanese War and World War II. During the Second Sino-Japanese War the National Revolutionary Army eventually organized itself into twelve Military Regions.

In December 1954, the existing six major military regions were reorganised into twelve regions: Shenyang, Beijing, Jinan, Nanjing, Guangzhou, Kunming, Wuhan (former Hubei MR), Chengdu, Lanzhou, Tibet, Xinjiang, and Inner Mongolia. The former Northwest Military Region, which became the Beijing Military Region, doubled as Beijing-Tianjin Garrison Command. Due to the tension in the Taiwan Straits, the State Council ordered the establishment of the Fuzhou Military Region on 22 April 1956. It included the provincial military districts of Fujian and Jiangsi, formerly under the Nanjing Military Region. The Fuzhou MR was officially established on 1 July 1956, with Ye Fei as its commander and political commissar.