Konstantin Josef Jireček (July 24, 1854 - January 10, 1918), son of Josef, taught history at Prague.

He entered the Bulgarian service in 1879, and in 1881 became minister of education at Sofia. In 1884 he became professor of universal history in Czech at Prague, and in 1893 professor of Slavonic antiquities at Vienna.

The bulk of Konstantin's writings deal with the history of the southern Slavs and their literature. They include a History of the Bulgars (Czech and German, 1876), The Principality of Bulgaria (1891), Travels in Bulgaria (Czech, 1888), etc.