Karel Prager was a Czech architect. He graduated in architecture from the Czech Technical University in 1949, beginning his career during the period of Socialist Realism. He then began to use new materials and structural elements; for example, his Institute of Macromolecular Chemistry in Prague, introduced a light curtain wall and a typical plan (low and wide entrance hall, with conference rooms, halls and restaurant, and high-rise office building) that was subsequently widely adopted by architects in Czechoslovakia.

Other examples of his innovative structural designs include the use of Vierendeel bridge trusses in his extension to the Federal Assembly building in Prague and the use of a heavy glass wall for acoustic purposes in the new auditorium at the National Theatre in Prague. In 1990-92 he designed the reconstruction of the House of Artists in Prague, and in 1993-4 he designed the reconstruction of the Cubist House at Black Madonna in Prague.