The 1906 United States Senate election in Kentucky was held on January 16, 1906, after an initial election on January 9, 1906. Democratic candidate Thomas H. Paynter was elected by the Kentucky General Assembly to the United States Senate. The election was held twice due to ambiguity in the law setting the election date.
The Democratic Party chose to select its candidate by legislative caucus. Incumbent senator J. C. S. Blackburn was defeated for renomination on January 2, 1906, by judge of the Kentucky Court of Appeals and former congressman Thomas H. Paynter.
The Republican Party chose to select its candidate by legislative caucus, with senator William H. Cox winning the nomination unanimously on January 3, 1906.