Dallas County is a county located in the U.S. state of Missouri. As of the 2010 census, the population was 17,071. Its county seat is Buffalo. The county was organized in 1842 as Niangua County and then renamed in 1844 for George M. Dallas, who served as Vice President under James K. Polk.

George Mifflin Dallas was an American politician and diplomat who served as mayor of Philadelphia from 1828 to 1829, the 11th vice president of the United States from 1845 to 1849, and U.S. Minister to the United Kingdom from 1856 to 1861.