The 1958 Wyoming gubernatorial election took place on November 4, 1958. Incumbent Republican Governor Milward Simpson ran for re-election to a second term. He was challenged by John J. Hickey, the former U.S. Attorney for the District of Wyoming and the Democratic nominee. Following a close campaign, Hickey narrowly defeated Simpson for re-election, winning just a narrow plurality because of a third-party candidate in the race. In an irony, just four years later, in the 1962 special U.S. Senate election, Simpson would defeat Hickey, avenging his loss in the gubernatorial election. To date, this is the last Wyoming gubernatorial election where an incumbent Republican was defeated.
Louis W. Carlson ran a campaign around legalizing gambling. Simpson attributed him defeat to his failure to win the traditional Republican Sheridan County. Voters in Sheridan County were displeased with Interstate 90 going from Gillette to Buffalo rather than between Gillette and Sheridan.