A political commissar is an officer appointed by a communist party to oversee a unit of the military. They were first used in the Red Army by Leon Trotsky, who faced the task of integrating Czarist officers and troops into the new Red Army, while ensuring their loyalty. The political commissars were appointed by the Communist Party to military units for the purpose of direct political propaganda, and to ensure that Party decisions were implemented. In this system, each unit had a political officer who was not responsible to the normal military chain of command, but instead answered to a separate chain of command within the Communist Party. The purpose of such a system is to ensure the loyalty of army commanders, and to prevent a possible coup d'etat. The political commissar had the authority to override any decision of the military officers, and to remove them from command if necessary. Therefore, sometimes the commissar usurped the functions of a regular military commander, but almost always that wasn't necessary — the mere presence of a commissar usually meant that military commanders would follow their directives, and the day-to-day duties of the political commissar generally involved only propaganda work and boosting the morale of the troops.

After 1942, the political officials in the army were no longer called commissars, their title becoming politruk (политру́к), an abbreviation for "political leader" and later zampolit, an abbreviation for "заместитель командира по политработе", "deputy of the commander in political works", the change reflecting the level of the authority: zampolit had no rights to interfere with operative orders of a commander. The position was abolished after the fall of the Soviet Union in 1991.

During the Russian Civil War, Joseph Stalin was the political commissar of the Western Front against the White Army forces of Baron Wrangel.

Military of China

The position of political commissar has also existed and still exists in the People's Liberation Army of China. Usually, the political commissar is a uniformed military officer, although this position has been used to give civilian party officials some experience with the military. The political commissar was head of a party cell within the military; however, military membership in the party was restricted to the lower ranks since the 1980s. Today the political commissar is largely responsible for administrative tasks such as civilian relations.