Third Army may refer to:
The Russian Third Army was a World War I Russian field army that fought on the Eastern theatre of war.
Field management was established in July 1914 at the headquarters of the Kiev Military District. The unit was disbanded in the beginning of 1918. At the beginning of the war the 3rd Army was composed of the IX, X, XI, XXI Army Corps.
The Third Army was originally based in Dubno. It comprised four Army Corps and three cavalry divisions, with the 3rd Caucasian Division joining them later. They were part of the invasion of Galicia, with the first stop for the staff officers was at Penyaki where they were made welcome by the servants of a house owned by a major in the Austrian Army. The building was set on fire by unknown people following their departure for Zolochev. Here the Army HQ was accommodated in a three-storey stone building which had previously been a bank.
The Japanese 3rd Army (第3軍, Dai-san gun) was an army of the Imperial Japanese Army based in Manchukuo as a garrison force under the overall command of the Kwantung Army during World War II, but its history dates to the Russo-Japanese War.
The Japanese 3rd Army was initially raised during the Russo-Japanese War under the command of General Nogi Maresuke. In the initial stages of the war, its primary mission was the Siege of Port Arthur. After the fall of that Russian stronghold, it was transferred north, where it played a crucial role in the subsequent Japanese drive towards Mukden in the closing stages of the war. It was disbanded at the end of the war.
The Japanese 3rd Army was raised again on January 13, 1938 in Manchukuo as a garrison force to guard the eastern borders against possible incursions by the Soviet Red Army. It afterwards came under the command of the Japanese First Area Army in July 1942. As the war situation deteriorated for the Japanese in southeast Asia, the more experienced units and much of the equipment of the IJA 3rd Army were transferred to other units.