The Ninth-of-May (1948) Constitution was the second constitution of Czechoslovakia, in force from 1948 to 1960. It came into force on 9 May, shortly after the communist seizure of power in the country on 25 February 1948. It replaced the 1920 Constitution.

Work on the new document had been underway since the summer of 1946. As a result, it was not a fully Communist constitution. It was superficially similar to its predecessor; indeed, several provisions were directly carried over from the earlier document. However, it contained a number of elements borrowed from the "Stalin Constitution" of the Soviet Union. The Soviet imprint on the final document was strong enough that President Edvard Bene refused to sign it and later resigned. It was flagrantly violated by the Communist Party of Czechoslovakia (KS), the government and many individuals throughout the period of its being in force, especially regarding the provisions on private ownership and human rights.

Since the country's liberation, there had been many disputes concerning nationalization, the relation of Czechs and Slovaks and other crucial issues. After the Communist take-over in February 1948, the Communist concept was largely applied. The constitution did not organize government administration under the Leninist principle of democratic centralism (a provision only incorporated in the following "socialist" 1960 Constitution of Czechoslovakia); indeed, it made no references to Communism or the KS. However, it did declare that Czechoslovakia had embarked on a "national and democratic revolution" that it intended to defend against "domestic and foreign reaction." It billed the 1948 coup d'etat as a defense of "the People's Democratic Order."

The constitution proclaimed Czechoslovakia a "people's democratic state" in which the people were "the sole source of all power." It declared that the economy of Czechoslovakia was based on nationalized industries, nationalized trade and a nationalized financial sector. The government sector was declared the basis of the economy, but it protected the private sector and cooperatives as well. It also granted a small degree of autonomy to Slovakia, which was given its own legislative body and governmental structure, although these were made subordinate to the central authorities in Prague. The parliament continued to be called the National Assembly, though the Senate was abolished.

Unlike most Communist constitutions, the Ninth-of-May Constitution did not replace the presidency with a collective body. It also afforded protections against arbitrary arrest; no one could be taken into custody without a warrant. On the other hand, the provisions enshrining civil rights were effectively neutered by a provision that forbade their use in order to make "statements and acts that constitute a threat to the independence, entirety, and unity of the State, the Constitution, the Republican form of government, or the People's Democratic Order" and allowed their restriction "when events occur that threaten in increased measure the independence, entirety, and unity of the State, the Constitution, the Republican form of government, and the People's Democratic Order, or public law and order." The constitutional guarantee of press freedom was rendered meaningless by provisions making movies and broadcasting state monopolies and giving the government sole power to decide who could publish periodicals. Judges were required to abide by both laws and government ordinances, thus taking away judges' right to strike down executive actions that did not accord with statutes.

Edvard Beneš (Czech pronunciation: [ˈɛdvard ˈbɛnɛʃ] (listen); 28 May 1884 – 3 September 1948) was a Czech politician and statesman who served as the president of Czechoslovakia from 1935 to 1938, and again from 1945 to 1948. He also led the Czechoslovak government-in-exile 1939 to 1945 during World War II.

As president, Beneš faced two major crises, which both resulted in his resignation. His first resignation came after the Munich Agreement and subsequent German occupation of Czechoslovakia in 1938, which brought his government into exile in the United Kingdom. The second came about with the 1948 Communist coup, which created the Czechoslovak Socialist Republic. Before his time as president, Beneš was also the first foreign affairs minister (1918–1935) and the fourth prime minister (1921–1922) of Czechoslovakia. A member of the Czechoslovak National Social Party, he was known as a skilled diplomat.