Charles Sealsfield was the pseudonym of German novelist Karl Anton Postl (3 March 1793 - 26 May 1864).

He was born at Popice (Poppitz) near Znojmo in Moravia. His schooling completed, he entered the Kreuzherrenorden in Prague, where he became a priest, but in the autumn of 1822 he fled to America, where he assumed the name of Charles Sealsfield. In 1826 he returned to Germany and published a book on America (Die Vereinigten Staaten von Nordamerika), which was followed by an outspoken criticism of Austria, written in English (Austria as it is, 1828) and published anonymously in London. Meanwhile he had returned to America, where he published his first novel, also in English, Tokeah, or the White Rose (1828). He now turned journalist, first in New York City and subsequently in Paris and London, as correspondent for various journals. In 1832 he settled in Switzerland, and in 1860 purchased a small estate near Solothurn. Here he died in May 1864. His will first revealed the fact that he was the former monk, Postl.

It is as a German novelist that he is best known. His Tokeah appeared in German under the title Der Legitime und die Republikaner (1838), and was followed by Der Virey und die Aristokraten (1835), Lebensbilder aus beiden Hemisphdren (1835-1837), Sturm-, Land- und Seebilder (1838), Das Kajutenbuch, oder. Nationals Charakteristiken (1842). Sealsfield occupies an important position in the development of the German historical novel at a period when Walter Scott's influence was beginning to wane. He endeavoured to widen the scope of historical fiction, to describe great national and political movements, without forfeiting the sympathy of his readers for the individual characters of the story.

Sealsfield's Gesammelte Werke appeared in 18 vols. (1843-1846); his chief novels are also to be obtained in modern reprints. See Kertbeny, Erinnerungen an Sealsfield (1864); L. Schmolle, Charles Sealsfield (1875); L. Hamburger, Sealsfield-Postl, bisher unveroffent-lichte Briefe (1879); A. B. Faust, Charles Sealsfield, der Dwhtet beider Hemispharen (1896).