The 1978 United States Senate election in Montana took place on November 7, 1978. Following the death of United States Senator Lee Metcalf on January 12, 1978, Montana Supreme Court Chief Justice Paul G. Hatfield was appointed to serve for the remainder of Metcalf's term. Hatfield opted to run for re-election, but was overwhelmingly defeated in the Democratic primary by United States CongressmanMax Baucus of the 1st congressional district. Baucus advanced to the general election, where he was opposed by Larry R. Williams, an author and the Republican nominee. Baucus ended up defeating Williams by a solid margin to win his first term in the Senate, and, following Hatfield's resignation on December 12, 1978, he began serving his first term in the Senate.