The 1966 United States Senate election in Arkansas took place on November 8, 1966. Incumbent U.S. Senator John L. McClellan was re-elected to a fifth term in office.
Because the Republican Party (or any other party) did not field a candidate in the general election, McClellan's primary victory was tantamount to election.
For the first time since 1954, Senator John McClellan faced a challenger for the Democratic nomination, Foster Johnson, a 51-year-old book salesman and political neophyte. McClellan did not stage a formal campaign for re-election and ignored his opponent. Johnson did win the support of organized labor in the state but attracted little attention to his campaign otherwise.
McClellan was unopposed in the general election. At this time, Arkansas law did not require tabulation of votes for unopposed candidates.