Humboldt University of Berlin (, abbreviated HU Berlin) is a public research university in the central borough of Mitte in Berlin, Germany. It was established by Frederick William III on the initiative of Wilhelm von Humboldt, Johann Gottlieb Fichte and Friedrich Ernst Daniel Schleiermacher as the University of Berlin ("Universität zu Berlin") in 1809, and opened in 1810, making it the oldest of Berlin's four universities. From 1810 until its closure in 1945, it was named Friedrich Wilhelm University (). During the Cold War the university found itself in East Berlin and was "de facto" split in two when the Free University of Berlin opened in West Berlin. The university received its current name in honour of Alexander and Wilhelm von Humboldt in 1949.