Born in Athens, Georgia, Kemp is a graduate of the University of Georgia. Prior to entering politics, he was a small business owner for several agribusiness, financial services, and real estate companies. In 2002 he was elected to the Georgia State Senate. In 2010, Kemp was appointed Secretary of State by Governor Sonny Perdue following the resignation of Karen Handel to run for governor. Kemp was subsequently elected to a full term as secretary of state in 2010, and he was reelected in 2014.

During Kemp's tenure as secretary of state, his office was affected by several accusations and controversies. In 2015, Kemp's office distributed the Social Security numbers and dates of birth of over 6.2 million Georgia voters. Kemp was the only secretary of state to reject help from the U.S. Department of Homeland Security to guard against Russian interference in the 2016 election. He also implemented Georgia's controversial "exact match" system for voter registration. Critics have described Kemp's actions as secretary of state as an example of democratic backsliding, although Kemp denies that he actively engaged in voter suppression.

In 2018, Kemp was a candidate for governor. After coming in second place in the Republican primary, he defeated Lieutenant Governor Casey Cagle in the Republican runoff with 69% of the vote. In the general election he faced Democratic nominee Stacey Abrams. Kemp notably refused to resign as secretary of state while campaigning for governor, a move that some critics claimed constituted a conflict of interest. Following the general election on November 6, Kemp was declared the winner with 50.2% of the vote. Abrams subsequently suspended her campaign on November 16. Kemp was inaugurated as governor in a public ceremony in Atlanta on January 14, 2019.

Kemp was born in Athens, Georgia, the son of William L. Kemp II. Kemp's grandfather, Julian H. Cox Sr., was a member of the Georgia Legislature. Kemp graduated from Athens Academy in 1983. He later graduated from the University of Georgia, where he majored in agriculture. Kemp was a home builder and developer before entering politics.

He served as a Georgia State Senator from 2003 to 2007 after defeating the Democratic incumbent, Doug Haines. In 2006, Kemp ran for Agriculture Commissioner of Georgia. He came second in the primary, but he lost the runoff to Gary Black. Kemp initially declared intent to run for State Senate District 47 when incumbent Ralph Hudgens planned to run for Congress in Georgia's 10th congressional district. Hudgens withdrew and ran for reelection, changing Kemp's plans. In early 2010, Kemp was appointed to Georgia Secretary of State by then-Governor Sonny Perdue. Kemp won the 2010 election for a full term as Georgia Secretary of State with 56.4% of the vote, to 39.4% for his Democratic opponent, Georganna Sinkfield. Four years later, Kemp was reelected.

Kemp rejects the conclusion by the United States Intelligence Community that Russia interfered in the 2016 election. Amid Russian interference in the 2016 election, Kemp denounced efforts by the Obama administration to strengthen the security of election systems, including improving access to federal cybersecurity assistance. He denounced the Obama administration's efforts, saying they were an assault on states' rights. After narrowly winning in the 2018 gubernatorial election, he resigned his office of Secretary of State in anticipation of becoming Governor. In March 2017, Kemp announced his candidacy in the 2018 Georgia gubernatorial election. In a field of six candidates, Kemp and Lieutenant Governor Casey Cagle came in the two top places in a six-way Republican primary in May 2018, advancing to a runoff election. Kemp ran against Democratic nominee Stacey Abrams, the minority leader of the Georgia House of Representatives, in the 2018 general election. During the gubernatorial campaign, Kemp embraced Trump-like policies and themes. Kemp ran on a policy of imposing a state spending cap, opposing Medicaid expansion, and implementing the "strictest" abortion laws in the country. Kemp favors repealing the Affordable Care Act, describing it as "an absolute disaster" and supports litigation seeking to eliminate the law's protections for persons with a pre-existing condition. He has said he would sign a bill of "religious freedom and restoration" vetoed twice by governor Nathan Deal, which would allow refusal of contraception to women or services to LGBT couples on the basis of religious beliefs. On December 4, 2018, U.S. Representative Elijah Cummings, the incoming chairman of the House Committee on Oversight and Government Reform, announced that he would like to call Kemp before Congress to testify about the fairness of his actions during the 2018 elections.

Kemp is married to Marty Kemp; they have three daughters. The family belongs to the Emmanuel Episcopal Church in Athens. Kemp's father-in-law was Bob Argo (1923-2016), an Athens insurance executive and longtime member of the Georgia House of Representatives. In May 2018, Kemp was sued for failure to repay $500k in business loans. The suit is related to Kemp having personally guaranteed $10 million in business loans to Kentucky based company Hart AgStrong, a canola crushing company. The company is under investigation after making guarantees using assets it did not own and repaying suppliers using proceeds from insurance settlements. An attorney for the Georgia Department of Agriculture has said these actions "may be a felony under Georgia law."