The Declaration of Conscience speech, by U.S. Senator from Maine, Margaret Chase Smith, is delivered in response to Joseph R. McCarthy's speech at Wheeling, West Virginia.

The Declaration of Conscience was a Cold War speech made by U.S. Senator from Maine, Margaret Chase Smith on June 1, 1950, less than four months after Senator Joseph McCarthy's "Wheeling Speech", on February 9, 1950. Her speech was endorsed by six other liberal-to-moderate Republicans. In it, she criticized national leadership and called for the country, the United States Senate, and the Republican Party to re-examine the tactics used by the House Un-American Activities Committee (HUAC) and Senator McCarthy. She stated the basic principles of "Americanism" were:

• The right to criticize;
• The right to hold unpopular beliefs;
• The right to protest;
• The right of independent thought.

Maine is a state in the New England region of the United States, and the northeasternmost state in the Contiguous United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Canadian provinces of New Brunswick and Quebec to the northeast and northwest, and shares a maritime border with Nova Scotia. Maine is the largest state in New England by total area, almost as large as the combined area of the remaining five states. Of the 50 U.S. states, it is the 12th-smallest by area, the 9th-least populous, the 13th-least densely populated, and the most rural. Maine's capital is Augusta, and its most populous city is Portland, with a total population of 68,408, as of the 2020 census.

Margaret Madeline Chase Smith was an American politician. A member of the Republican Party, she served as a U.S. representative (1940–1949) and a U.S. senator (1949–1973) from Maine. She was the first woman to serve in both houses of the United States Congress. A Republican, she was among the first to criticize the tactics of Joseph McCarthy in her 1950 speech "Declaration of Conscience".