Margaret Madeline Chase Smith (December 14, 1897 – May 29, 1995) 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, and the first woman to represent Maine in either. A moderate Republican, she is perhaps best remembered for her 1950 speech, "Declaration of Conscience," in which she criticized the tactics of McCarthyism.

Smith was an unsuccessful candidate for the Republican nomination in the 1964 presidential election, but was the first woman to be placed in nomination for the presidency at a major party's convention. Upon leaving office, she was the longest-serving female Senator in history, a distinction that was not surpassed until January 5, 2011, when Senator Barbara Mikulski was sworn in for a fifth term.