The 2006 United States Senate election in Montana was held November 7, 2006. The filing deadline was March 23; the primary was held June 6. Incumbent Republican Senator Conrad Burns ran for re-election to a fourth term, but lost to Democrat Jon Tester by a margin of 0.87%, or 3,562 votes out of 406,505 cast. This made the election the second-closest race of the 2006 Senate election cycle, behind only the election in Virginia.