Karl Postl (1769–1818) was an Austrian painter who had a career in Prague during the early 19th century. An instructor at the Prague Academy, he also served as a scene painter for the Estates Theatre. Most of his work was in the field of graphic design, but a few paintings by his hand exist; some are in the collection of the National Gallery in Prague. Antonín Mánes was his main pupil.
Karl was born into a count's family, Paar in Bechyni. He studied painting and graphic design at the Academy in Vienna. From the late 18th century, he set up a studio in Prague. He was promoted as the first director of drawing at the Academy by Czech patrons, but preference was given to Josef Bergler. From 1806 to 1817, that is, until his untimely death, he taught landscape painting and graphic vista at the Academy in Prague. His students included Josef Šembera, Vincenc Morstadt, Joseph Frederick Zwettler and Antonin Manes, the latter also became successor at the Academy. Then from 1804, Postl worked as a theatrical scene painter at the Estates Theatre, where he was later replaced by Antonin Machek.
He died prematurely of pulmonary tuberculosis. He is buried at the Olšany Cemetery in Prague.
His work blends classicism and romanticism patterns both Viennese and French (inspired by the likes of Claude Lorrain and Nicolas Poussin). His landscape work was generally focused on panoramic views of Prague, which were often presented in graphic albums. He was also a skilled portraitist. He also participated in the creation of postcards for some spa towns . His paintings are shown primarily in the collections of the National Gallery and the Museum of Prague.