The Biblioteca Nazionale Braidense or Braidense National Library, usually known as the Biblioteca di Brera, is a public library in Milan, in northern Italy. It is one of the largest libraries in Italy. Initially, it contained large historical and scientific collections before it was charged with the legal deposit of all publications from Milan. Since 1880, it has had the status of a national library and is today one of the 47 Italian State libraries.

Legal deposit is a legal requirement that a person or group submit copies of their publications to a repository, usually a library. The number of copies required varies from country to country. Typically, the national library is the primary repository of these copies. In some countries there is also a legal deposit requirement placed on the government, and it is required to send copies of documents to publicly accessible libraries.