Karl Christian Sigismund Bernhardi was a German librarian and politician.

Karl August Bleibtreu was a German writer who promoted naturalism in German literature. He was noted for his aggressive and dogmatic style of criticism, linked to a nationalistic and sometimes antisemitic agenda. His later work was heavily influenced by Nietzsche's theory of the übermensch.

Karl Bosl was a German regional historian. He held the chair for Bavarian regional history at the Ludwig Maximilian University of Munich from 1960 until his retirement in 1977.

Karl August Böttiger was a German archaeologist and classicist, and a prominent member of the literary and artistic circles in Weimar and Jena.

Karl Maria Prosper Laurenz Brandi was a German historian.

Karl Christian Ernst Graf von Bentzel-Sternau, pseud. Horatio Cocles, was a German statesman, editor and writer.

Karl Christian Friedrich Krause was a German philosopher whose doctrines became known as Krausism. Krausism, when considered in its totality as a complete, stand-alone philosophical system, had only a small following in Germany, France, and Belgium, in contradistinction to certain other philosophical systems that had a much larger following in Europe at that time. However, Krausism became very popular and influential in Restoration Spain not as a complete, comprehensive philosophical system per se, but as a broad cultural movement. In Spain, Krausism was known as "Krausismo", and Krausists were known as "Krausistas". Outside of Spain, the Spanish Krausist cultural movement was referred to as Spanish Krausism.

Karl Christian Planck (January 17, 1819 – June 7, 1880) was a German philosopher.

Karl Dedecius was a Polish-born German translator of Polish and Russian literature.

Karl Dietrich Leonhard Engel was a German musician and writer.