John Clark was an American planter, politician, and slaveholder. He was the 31st Governor of the U.S. state of Georgia, from 1819 to 1823. As governor, he prevailed in the U.S. Supreme Court case Ex parte Madrazzo, a dispute over whether a claim of ownership of a group of enslaved people could be enforced against the state. He also advocated for presidential electors to be elected by popular vote as seen in many of his bills, culminating in the 1824 Georgia Popular Vote Referendum.