Martynas Mažvydas National Library of Lithuania (Lithuanian: Lietuvos nacionalinė Martyno Mažvydo biblioteka) is a national cultural institution which collects, organizes and preserves Lithuania's written cultural heritage content, develops the collection of Lithuanian and foreign documents relevant to research, educational and cultural needs of Lithuania, and provides library information services to the public.

Martynas Mažvydas National Library goals are accumulation and preservation of the Lithuanian documentary cultural heritage for the future generations and ensuring its access, active participation in the knowledge society creation process, development of its activities and services using modern information technologies with the purpose to assist the learning and development processes of Lithuanian people, providing methodological support for Lithuanian libraries, carrying out research in library science, bibliography, information science and bibliology, evolving library science theory and practice and strengthening the dynamics of integration into the global library science processes.

It started in Kaunas as the State Central Bookstore and in 1963 it was transferred to Vilnius, the capital of Lithuania.

In 1992 the first cooperation agreement between the national libraries of the Baltic States (Lithuania, Latvia and Estonia) was signed.

Its open collection contains the personal library of Prof. Vytautas Landsbergis, the Chairman of the Supreme Council and Reconstituent Seimas of Lithuania.

The library hosts various national and international cultural, social, educational, scientific and political events, meetings and conferences as well as book presentations and movie screenings.

The library offers a variety of educational activities and training courses for adults, children and youth.

As part of the project "Promotion of Smart Use of the Web Through the Upgraded Facilities of Public Internet Access" the library has set up a workplace for visually impaired visitors.

The largest part of the manuscripts collection consists of the archives of private persons (Lithuanian writers, scientists, artists, cultural activists who lived in Lithuania and abroad) from the 19th and 20th centuries.

It also stores the memorial collections entrusted to the library by various prominent figures of the Lithuanian history: the Lozoraitis family of diplomats, the philosopher Antanas Maceina, the poet Tomas Venclova and others.

Biographies of prominent Lithuanian Jews, Jewish cookbooks, reference books, encyclopaedias, dictionaries, and bibliographic publications are also stored here.

Exceptionally valuable is the collection of Lithuanian shellac records (2,566 titles) dating back to early 20th century.