The 1918 United States Senate election was held on November 5, 1918. Incumbent Democratic U.S. Senator Henry F. Hollis declined to run for re-election. Governor Henry W. Keyes narrowly won the Republican primary over former Governor Rolland H. Spaulding and faced former U.S. Representative Eugene E. Reed, the Democratic nominee, in the general election. Keyes ultimately defeated Reed, winning the first of his three terms in the U.S. Senate.