The Smith Act, officially known as the Alien Registration Act of 1940, was a U.S. law that made it a criminal offense to advocate the violent overthrow of the government or to belong to any organization that did so. This legislation became particularly significant during the period of McCarthyism and the Red Scare, as it was used to prosecute individuals accused of being Communists or sympathizers, reflecting the heightened fears of subversion and dissent in America during the Cold War.