The library was established by a decree released by the Empress Maria Theresa in 1774. Around 637 books, spared by a fire in the previously dissolved Jesuit college in Ljubljana, were henceforth available for public use in the newly established library of the Ljubljana Lyceum.
The Lyceum library was legally entitled to receive legal deposit copies from the province of Carniola as early as 1807. During the French occupation, this edict applied to all of the Illyrian provinces. After the abolition of the Lyceum in 1850 the library became the main reference library of the province.
After World War I, in 1919, it was renamed the State Reference Library, thus becoming the central library of Slovenia with the right to receive legal deposit copies from that area. In 1921, the library became the State Library, and deposit of publications from all the regions of former Yugoslavia started to pour in.
With the foundation of the first Slovenian university in Ljubljana, the library served also as the central university library. Unfortunately, it had to operate provisionally in the limited confines of an adapted part of the Lyceum in Poljane Street. Therefore, Ljubljana as a university city could only offer eighteen reader seats in its university library. The library was named the University Library in 1938 according to the regulations of both the University Act and the General University Decree.
Plans for the new University Library were created between 1930 and 1931 by the architect Jože Plečnik. However, claims for a new Slovenian university library encountered resistance by the authorities, which were then based in Belgrade. Persistent student protests and demonstrations nevertheless brought an end to it. As a result, in 1941 the University Library moved into a new monumental building in the immediate vicinity of the University. Plečnik’s Library is an exquisite cultural monument.
After liberation in 1945, the University Library was legally recognised as the Slovenian national library and it was again renamed the National and University Library.