The Third Czechoslovak Republic, officially the Czechoslovak Republic, was a sovereign state from April 1945 to February 1948 following the end of World War II.

After the fall of Nazi Germany, the country was reformed and reassigned coterminous borders as its pre-war predecessor state, First Czechoslovak Republic; it likewise restored the predecessor's international recognition. Due to the rise of the Communist Party of Czechoslovakia (KSČ), Czechoslovakia fell within the Soviet sphere of influence, and this circumstance dominated any plans or strategies for post-war reconstruction. Consequently, the political and economic organisation of Czechoslovakia became largely a matter of negotiations between Edvard Beneš and the Communist Party members exiled in Moscow.

As early as July 1947, Soviet leader Joseph Stalin intervened against Czechoslovak participation in the Marshall Plan, and Beneš's concept of a so-called "bridge" between East and West was negated, which meant that the alliance treaty with France was not implemented. Moscow expressed doubts about the declared parliamentary path to socialism and subsequently called on the Communist Party of Czechoslovakia to take power quickly. In February 1948, the Communists finally managed to provoke non-Communist parties into attempting to change the previous coalition government of Klement Gottwald and used the situation for a political coup. Czechoslovakia thus became part of the Soviet sphere of interest and later also of Stalin's power bloc.

In February 1948, the Communist Party seized full power in a coup d'état. Despite the country's official name remaining the Czechoslovak Republic until 1960, when it was changed to the Czechoslovak Socialist Republic, events of February 1948 are considered the end of the Third Republic.

The Third Republic came into being in April 1945 with the creation of the Košice Programme. All of the remaining German armed forces also surrendered to the Allies on 8 May 1945. President Beneš flew from his exile in London to Košice in eastern Slovakia, which had been taken by the Red Army and which became the temporary capital. In Košice the new National Front government was formed, based on discussions dating back to 1943, with Beneš remaining president, Zdeněk Fierlinger becoming prime minister with Klement Gottwald as deputy premier.

In the National Front coalition, three socialist parties—KSČ, Czechoslovak Social Democratic Party, and Czechoslovak National Social Party—predominated. The Slovak Popular Party was banned as a collaborationist with the Nazis. Other conservative yet democratic parties, such as the Republican Party of Farmers and Peasants (RSZML), were prevented from resuming activities in the postwar period. Certain acceptable nonsocialist parties were included in the coalition; among them were the Catholic People's Party (in Moravia) and the Slovak Democratic Party.

The government moved back to Prague after its liberation on 10 May. Beneš was pressured by the Soviet Union to grant them the Carpathian Ruthenia territory as a sort of war reparation, and a treaty was signed on 29 June 1945 annexing it to the Ukrainian SSR of the Soviet Union.

Industries, employing 61.2 percent of the industrial labour force, were nationalised.^{[citation needed]}