Clarke County is a county located in the U.S. state of Iowa. As of the 2020 census, the population was 9,748. The county seat is Osceola. The county was formed in January 1846, one of twelve counties established by legislative action in a comprehensive act. It was named for James Clarke, a Governor of the Iowa Territory.

James Clarke was the third Governor of Iowa Territory from November 18, 1845 until December 3, 1846, being appointed to the office, as a Democrat, by President James Polk. Born in Greensburg, Pennsylvania, Clarke was secretary of Iowa Territory from 1839–1841 and mayor of Burlington, Iowa from 1844-1845. Clarke was the son-in-law of Henry Dodge, whom Fort Dodge, Iowa, is named in his honor. Clarke County, Iowa was named after James Clarke. He died in Burlington.