Christian Weise, also known under the pseudonyms Siegmund Gleichviel, Orontes, Catharinus Civilis and Tarquinius Eatullus, was a German writer, dramatist, poet, pedagogue and librarian of the Baroque era. He produced a large number of dramatic works, noted for their social criticism and idiomatic style. In the 1670s he started a fashion for German "political novels". He has also been credited with the invention of the mathematical Euler diagram, though this is uncertain.