Hardtner is a city in Barber County, Kansas, United States. As of the 2010 census, the city population was 172.
On June 2, 1929, a tornado struck Hardtner, causing minor damage. The tornado was notable since it moved very slowly, yielding some of the highest quality photographs of a tornado to that date.
Hardtner is located at 37°0′48″N 98°38′56″W / 37.01333°N 98.64889°W / 37.01333; -98.64889 (37.013263, -98.648775). According to the United States Census Bureau, the city has a total area of 0.3 square miles (0.8 km²), all of it land.