Muriel Fay Humphrey Brown (née Buck; February 20, 1912 – September 20, 1998) was an American politician who served as the second lady of the United States from 1965 to 1969, and as a U.S. Senator from Minnesota in 1978. She was married to the 38th vice president of the United States, Hubert Humphrey. Following her husband's death, she was appointed to his seat in the United States Senate, serving for most of the year 1978, thus becoming the first woman to serve as a senator from Minnesota. After leaving office, she remarried and took the name Muriel Humphrey Brown.