Thomas David Patrick O'Malley Sr. (March 24, 1903 – December 19, 1979) was an American Democratic politician from Milwaukee, Wisconsin. He served three terms in the United States House of Representatives, representing Wisconsin's 5th congressional district from 1933 through 1939, and was later an appointee in the United States Department of Labor. His father, Thomas J. O'Malley, was the 26th lieutenant governor of Wisconsin.

Thomas O'Malley was born in Milwaukee, Wisconsin, on March 24, 1903. He was raised and educated in Milwaukee, before attending Loyola University Chicago and the Y.M.C.A. College of Liberal Arts in Chicago. At an early age he became engaged in politics with the Democratic Party, due to his father's political activity.

He first sought elected office in 1928, running for United States House of Representatives in Wisconsin's 5th congressional district. He prevailed in the Democratic primary, but came in a distant third in the general election, behind the Socialist incumbent, Victor L. Berger, and the Republican victor, William H. Stafford.^[1] He made another attempt in 1930, but lost again to the Republican Stafford.^[2]

Two years later, O'Malley was elected as a delegate to the 1932 Democratic National Convention. He was one of only two delegates from Wisconsin who refused to vote for Franklin D. Roosevelt, remaining loyal to Al Smith. At the Fall general election, O'Malley ran again for Congress, and this time prevailed in the Democratic wave election, and went on to serve in the 73rd United States Congress.^[3]

O'Malley faced a bitter primary race running for re-election in 1934, but managed to prevail against four Democratic challengers. He went on to win his second term with just 34% of the vote, with the Wisconsin Progressive Party emerging as a fourth major party in the district.^[4] He faced multiple challengers in both 1936 and 1938, surviving again in 1936, but losing in 1938.^[5][6]

O'Malley's most noteworthy contribution during his six years in Congress was likely the Johnson–O'Malley Act, to subsidize education, medical facilities, and other services for the Native American population. It passed in 1934.^[7]

After leaving Congress, he was appointed regional director for the Wages and Hours division of the United States Department of Labor. His region comprised Wisconsin, Illinois, and Indiana, and he ultimately served in this role for another 18 years, retiring in 1956. During those years, he moved to Chicago, Illinois, where he resided for much of the rest of his life.^[8]

He died on December 19, 1979, at Northwestern Memorial Hospital in Chicago after suffering a blood clot.^[8]