The Ninth-of-May (1948) Constitution (Czech: Ústava Československé republiky; Slovak: Ústava Československej republiky) was a communist state constitution and 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 Beneš refused to sign it and later resigned. It was flagrantly violated by the Communist Party of Czechoslovakia (KSČ), the government and many individuals throughout the period of its being in force, especially regarding the provisions on private ownership and human rights.