The 1974 United States Senate election in Colorado took place on November 5, 1974. Incumbent Republican U.S. Senator Peter Dominick ran for re-election to a third term in office, but was defeated by Democrat Gary Hart.
As of 2024, this is the last time that an incumbent Senator from Colorado lost re-election for this seat, and the last time that El Paso County voted for the Democratic candidate in a Senate election.