The 1966 Idaho gubernatorial election was held on November 8. Republican nominee Don Samuelson defeated Democratic nominee Cecil Andrus with 41.4% of the vote in a four-way race.

Cecil Dale Andrus was an American politician who served as 26th and 28th governor of Idaho, for a total of fourteen years. A Democrat, he also served as U.S. Secretary of the Interior from 1977 to 1981 during the Carter Administration. Andrus lost his first gubernatorial election in 1966 but won four and his fourteen years as governor is the most in state history. He is the most recent Democrat to have held the office.