Humboldt University of 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 (German: Friedrich-Wilhelms-Universität). 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.

The university is divided into nine faculties, including its medical school shared with the Free University of Berlin, has a student enrollment of around 32,000 students, and offers degree programmes in some 189 disciplines from undergraduate to postdoctorate level. Its main campus is located on the Unter den Linden boulevard in central Berlin. The university is known worldwide for pioneering the Humboldtian model of higher education, which has strongly influenced other European and Western universities.

It was regarded as the world's preeminent university for the natural sciences during the 19th and early 20th century, as the university is linked to major breakthroughs in physics and other sciences by its professors, such as Albert Einstein. Past and present faculty and notable alumni include 57 Nobel Prize laureates (the most of any German university by a substantial margin), as well as eminent philosophers, sociologists, artists, lawyers, politicians, mathematicians, scientists, and Heads of State; among them are Albert Einstein, Karl Marx, Friedrich Engels, Otto von Bismarck, W. E. B. Du Bois, Angela Davis, Arthur Schopenhauer, Georg Wilhelm Friedrich Hegel, Walter Benjamin, Max Weber, Georg Simmel, Karl Liebknecht, Ernst Cassirer, Heinrich Heine, Max Planck and the Brothers Grimm.

As one of Germany's most prestigious institutions of higher education, Humboldt University of Berlin has been conferred the title of "University of Excellence" under the German Universities Excellence Initiative.