The 1st Czechoslovak Army Corps (Czech: První československý armádní sbor, Slovak: Prvý československý armádny zbor), also known as Svoboda's Army (Czech: Svobodova armáda, after its commander Ludvík Svoboda), was a military formation of the Czechoslovak Army in exile fighting on the Eastern Front alongside the Soviet Red Army in World War II.

The corps was the largest of the Czechoslovak units that fought on the Soviet side on the Eastern Front.

The 1st Czechoslovak Independent Field Battalion, formed in Buzuluk in the Urals, was the first foreign unit fighting alongside the Red Army in Soviet Union. It was formed from former members of the Czechoslovak Legion, Czechoslovak citizens (mostly refugees) living in the Soviet Union, Slovak prisoners-of-war and defectors, and Volhynian Czechs (Soviet citizens of Czech origin). Lieutenant-colonel Ludvík Svoboda was appointed to become the commander of the unit on 15 July 1942.

Despite the plans of the Czechoslovak government-in-exile in the United Kingdom, who intended to keep the unit intact to help with the future liberation of the Czechoslovakia, the officers of the battalion tried to bring the unit into the fight as soon as possible. After sending a personal letter to Joseph Stalin, they eventually succeeded and the battalion was sent into action. Notably, it took part in the defensive battle of Sokolovo, a part of the larger Third Battle of Kharkov, in March 1943. At the time, it was one of the most well armed infantry battalions on the East Front – fully equipped with automatic guns and semiautomatic infantry weapons. However, the battalion lacked heavier anti-tank weapons and artillery, which was to be provided by supporting Soviet units. Because of this, during the battle, when facing parts of the German armored division, the battalion suffered heavy losses and was later withdrawn from the front line.

In May 1943, the remnants of the 1st Czechoslovak Independent Field Battalion and the 1st Czechoslovak Reserve Regiment were reorganized into 1st Czechoslovak Independent Brigade. The reinforcements were largely Rusyn and Ukrainian prisoners released from the Gulag camps. The brigade played a key role in the 1943 battle of Kiev, and its troops were some of the first to reach the center of the Ukrainian capital city. The brigade suffered only low losses: 33 dead and missing, 82 wounded. At the time the brigade had a strength of 3,348 personnel.

Large parts of the Ukrainian Soviet Socialist Republic had been liberated by 1943 and 1944, allowing the Czechoslovak units to recruit Volhynian Czechs who were technically Soviet citizens. Around 12,000 enlisted, becoming the core of the post-war Czechoslovak Army. At the same time, thousands of Slovak prisoners of war, captured or deserted from Slovak Army, were regrouped and trained as the new parachute unit. This enabled to build the army corps.

The corps was created on April 10, 1944, at Chernivtsi and his headquarters moved to Sadagura. The 1st Czechoslovak Army Corps consisted of three (later four) infantry brigades and of tank, artillery, engineer and other support units. Some of these units were later reorganized into higher independent units, such as Tank Brigade and Mixed Air Division. While most of the Czechoslovak units served as part of the Corps, some may have been detached for operations with Red Army formations and units as required.

In late autumn 1944, when parts of Czechoslovakia (Ruthenia and eastern Slovakia) were already liberated, a new infantry brigade was formed and the support units transformed into higher units.