The Securities Act of 1933, also known as the 1933 Act, the Securities Act, the Truth in Securities Act, the Federal Securities Act, and the '33 Act, was enacted by the United States Congress on May 27, 1933, during the Great Depression and after the stock market crash of 1929. It is an integral part of United States securities regulation. It is legislated pursuant to the Interstate Commerce Clause of the Constitution.

Securities regulation in the United States is the field of U.S. law that covers transactions and other dealings with securities. The term is usually understood to include both federal and state-level regulation by governmental regulatory agencies, but sometimes may also encompass listing requirements of exchanges like the New York Stock Exchange and rules of self-regulatory organizations like the Financial Industry Regulatory Authority (FINRA).