The 1938 United States Senate election in Oklahoma took place on November 8, 1938. Incumbent Democratic Senator Elmer Thomas ran for re-election to a third term. He faced a spirited challenge in the Democratic primary from Congressman Gomer Smith and Governor E. W. Marland, but won the nomination with a slim plurality. In the general election, Thomas faced former State Senator Harry O. Glasser, the Republican nominee. Despite the nationwide trend favoring Republicans, Thomas overwhelmingly won re-election.