Williams was born in Raymond near Jackson. He graduated from Hinds Junior College in 1938, attended the University of Mississippi at Oxford, and graduated from Jackson Law School in 1940. In November 1941, he enlisted with the U.S. Army Air Corps and served as pilot during World War II; however, he retired from active service after losing the lower part of his left arm after a bomber crash in 1944. In 1946, Williams was elected to the U.S. House of Representatives as a Democrat. He was the youngest U.S. Representative to have been elected from Mississippi.
Williams advocated states' rights and segregation. He walked out of the 1948 Democratic National Convention in Philadelphia and supported Strom Thurmond's presidential campaign, whose primary platform was racial segregation. After the Supreme Court made its Brown v. Board of Education ruling in May 1954 which outlawed racial segregation in schools, Williams made a speech on the House floor branding the day 'Black Monday'. Williams supported the Democratic party's presidential campaign in 1952, and supported unpledged Democratic electors in 1956 and 1960. But in 1964, Williams endorsed Republican Barry Goldwater for President and helped raise funds for him in Mississippi. Because of his activities for Goldwater, the national Democratic Party stripped Williams of his House seniority.
In 1967, Williams ran for governor. The field of candidates was large, including one former governor (Ross Barnett) and two future Governors (William Winter and William Waller). In the primary, Williams claimed that former Governor Ross Barnett made a secret deal with the Kennedys. He finished second to the moderate candidate Winter. In the runoff, Williams defeated Winter by 61,000 votes. In the general election, Williams handily defeated Republican Rubel Phillips, who made the second of his two losing campaigns for governor.
During Williams's term as governor, Mississippi experienced the desegregation of its school system through a federal court order. Williams, despite his background as a strong segregationist, refused to defy the court.