Alte Bibliothek, Baroque library in Berlin-Mitte, Germany.

Alte Bibliothek is a pale-stone baroque building on Bebelplatz, built 1775–1780 by Georg Christian Unger after Joseph Emanuel Fischer von Erlach's design for the Michaelertrakt of the Vienna Hofburg. Its concave facade curves inward, with a projecting central section of tall columns and arched windows, statues and a winged figure along the balustrade, and the inscription HUMBOLDT-UNIVERSITAET across the centre. A black clock on a stone pedestal stands in front.

Frederick the Great ordered the building in 1775 as part of his Forum Fridericianum; Georg Christian Unger built it to 1780 using Joseph Emanuel Fischer von Erlach's unpublished Vienna Hofburg design, so Berlin's copy predates Vienna's 1889–1893 version. In 1784 the Royal Library moved in with 150,000 volumes. After the library left in 1910 the building became university lecture halls; bombed in the war, it was rebuilt 1963–1969.

Berliners nicknamed the building "Kommode" (chest of drawers) for its curved facade. Over the portal stands the Latin motto "nutrimentum spiritus" (nourishment of the spirit), a translation that drew criticism; locals joked "Spiritus is ooch 'n Nahrungsmittel". In autumn 1895 Lenin read in the library, and the GDR later named the room Lenin-Lesesaal in memory.

The Alte Bibliothek stands at Bebelplatz 2, on the Forum Fridericianum in Berlin-Mitte, a short walk from Unter den Linden and the Staatsoper. The building now houses the Law Faculty of the Humboldt-Universität, so the interior is in use for teaching; visitors see the reconstructed baroque facade and the inscription over the portal from the square. The oval staircase with its wrought-iron rococo railing, moved from a demolished house on Brüderstraße 8, is inside.

The Berlin copy of Joseph Emanuel Fischer von Erlach's design for the Michaelertrakt of the Vienna Hofburg was built more than a century before the Viennese original, which was only realised in modified form between 1889 and 1893. Frederick the Great had ordered Unger to use the published, unexecuted copperplate plans.