The Maryland gubernatorial election of 1966 was held on November 8, 1966. Incumbent Democratic Governor J. Millard Tawes was unable to seek a third term in office. In the election to succeed him, George P. Mahoney, a controversial segregationist, emerged from the Democratic primary due to splintered support for the two major candidates. Baltimore County Executive Spiro Agnew, who would later go on to be selected by Richard M. Nixon as his running mate in 1968, was nominated by the Republican Party as their gubernatorial candidate. Mahoney and Agnew squared off, along with independent candidate Hyman A. Pressman. Ultimately, Agnew was victorious over Mahoney, with Pressman a distant third. This year would be the last time that the state of Maryland elected a Republican governor until 2002.
Baltimore paving contractor and perennial candidate George P. Mahoney won the Democratic primary on a segregationist platform, which was possible due to the presence of several strong candidates. Mahoney's slogan, "Your home is your castle--protect it", as well as his stance on many civil rights issues, prompted Baltimore City Comptroller Hyman A. Pressman to enter the race as an independent candidate. Mahoney's controversial stances caused many in the Maryland Democratic Party to split their support between Agnew, which was possible due to his socially progressive views, and Pressman, which enabled Agnew to win the election with a plurality, taking 70% of the black vote.