The 1978 United States Senate election in Wyoming was held on November 7, 1978. Incumbent Republican Senator Clifford Hansen declined to seek a third term in office. Former State Representative Alan K. Simpson, the son of former Senator Milward Simpson, won a contested Republican primary and faced Raymond B. Whitaker, the 1960 Democratic nominee for the Senate, in the general election. Despite a favorable environment for Republicans nationwide, Simpson's performance decreased considerably from Hansen's 1972 landslide. Nonetheless, he easily defeated Whitaker, winning 62% of the vote to Whitaker's 38%.