The National Széchényi Library (Hungarian: Országos Széchényi Könyvtár) (OSZK) is a library in Budapest, Hungary. It is one of two Hungarian national libraries, the other being University of Debrecen Library.
The library was founded in 1802 by the highly patriotic Hungarian aristocrat Count Ferenc Széchényi. Széchényi traveled the world buying Hungarian books, which he assembled and donated to the nation. In the following year the public library was opened in Pest. Széchényi's example resulted in a nationwide movement of book donations to the library.
In 1808, the Hungarian National Assembly ("Diet") created the Hungarian National Museum to collect the historical, archaeological and natural relics of Hungary. The Museum was merged into the Library and for the last 200 years this is how it has existed, a national depository for written, printed and objective relics of the Hungarian past.
In 1846, the Hungarian National Museum moved into its new building but it was not until 1949 that the Library became a separate entity again, with its current name. In 1985, the library moved to its new home at the Buda Castle Palace. The NSZL works on its catalogue's semantic availability.
In 2014, a Hungarian librarian discovered four pages of Mozart's original score (autograph) of the sonata in Budapest's National Széchényi Library. Until then, only the last page of the autograph survived.[A] The paper and handwriting of the four pages matched that of the final page of the score, held in Salzburg. Zoltán Kocsis gave the first performance of the discovered score in September 2014.