Warren Grant "Maggie" Magnuson (April 12, 1905 – May 20, 1989) was an American lawyer and politician. A member of the Democratic Party, he served as a U.S. Representative (1937–1944) and a U.S. Senator (1944–1981) from Washington. He served over 36 years in the Senate, and was the most senior member of the body during his final two years in office. He earned a Bachelor of Laws degree from the University of Washington School of Law in 1929, and became active in politics in 1928, volunteering for A. Scott Bullitt for governor and Al Smith for president. In 1929, Magnuson was admitted to the bar and joined the law office of Judge Samuel Stern in Seattle. He served as special prosecutor for King County in 1932, investigating official misconduct. He was a leading supporter of repealing state Prohibition laws and establishing the state Liquor Control Board. From 1933 to 1934, Magnuson served as a member of the Washington House of Representatives from the Seattle-based 37th Legislative District. As a state legislator, he sponsored the first unemployment compensation bill in the nation. He was a delegate to the state constitutional convention in 1933. He briefly served as Assistant United States District Attorney before being elected prosecuting attorney of King County, serving from 1934 to 1936.
Magnuson was first elected to the House of Representatives in 1936, filling a vacancy caused by the sudden death of fellow Democrat Marion Zioncheck on August 7, 1936. In 1937, along with senators Homer Bone and Matthew Neely, he introduced the National Cancer Institute Act, which was signed into law by President Franklin D. Roosevelt on August 5 of that year. Magnuson won re-election in 1938, 1940, and 1942. In 1944, he successfully ran for the U.S. Senate. He was appointed on December 14, 1944, to fill the vacancy created by Homer Bone's appointment to the Ninth Circuit Court of Appeals, thus resigning from the House and starting his service in the Senate a month early. He was re-elected in 1950, 1956, 1962, 1968, and 1974. He served on the Senate Commerce Committee throughout his tenure in the Senate, and the Senate Appropriations Committee during his final term.