《美利堅合眾国宪法》第十八修正案 (英語：Eighteenth Amendment to the United States Constitution）簡稱「第十八修正案」（Amendment XVIII），是美国宪法历史上宣告酒類釀造、運輸和銷售是違法的一个修正案[註 1]，實質上頒布了酒類飲料的禁制令。另外制定的沃爾斯泰德法則頒布了執行第十八修正案的細節，並定義何種「致醉」酒類飲料是被禁止的，以及何種是被排除於禁酒令外的，如藥用或宗教儀式用酒類。這修正案是第一個設定生效緩衝期限、並是第一個設定同意期限的修正案。第十八修正案在1919年1月16日達到足夠數量的州認可，並於1920年1月17日生效。
Section 1. After one year from the ratification of this article the manufacture, sale, or transportation of intoxicating liquors within, the importation thereof into, or the exportation thereof from the United States and all territory subject to the jurisdiction thereof for beverage purposes is hereby prohibited.
Section 2. The Congress and the several States shall have concurrent power to enforce this article by appropriate legislation.
Section 3. This article shall be inoperative unless it shall have been ratified as an amendment to the Constitution by the legislatures of the several States, as provided in the Constitution, within seven years from the date of the submission hereof to the States by the Congress.
