The Eighteenth Amendment may refer to:

• Eighteenth Amendment to the United States Constitution, which established Prohibition
• Eighteenth Amendment of the Constitution of India, 1966 amendment which clarified the meaning of "state"
• Eighteenth Amendment of the Constitution of Ireland, which permitted the state to ratify the Amsterdam Treaty
• Eighteenth Amendment to the Constitution of Pakistan, which reduced the powers of the President of Pakistan
• Eighteenth Amendment of the Constitution of South Africa, which made South African Sign Language an official language
• Homer vs. the Eighteenth Amendment, an episode of the television series The Simpsons

This disambiguation page lists articles associated with the title Eighteenth Amendment.
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