GIESSEN, a town of Germany, capital of the province of Upper Hesse, in the grand duchy of Hesse, at the confluence of the Wiesbeck with the Lahn, and on the railway from Frankfurt to Cassel, thirty-three miles N.N.W. of the former city. The fortifications which formerly surrounded Giessen have been destroyed, and their site converted into promenades. The town itself is old and generally ill built, but contains some good edifices, as the castle, now the seat of the provincial government, the university buildings, arsenal, town-hall, and the new town church. The university was founded in 1607, and has a library of 40,000 volumes, a botanic garden, observatory, museum of natural history, &c. Its school of organic chemistry has become famous under Professor Liebig, and is frequented by students from all parts of Europe. Pop. 9049.