NAPLE Sister Libraries programme was established by the NAPLE (National Authorities on Public Libraries in Europe) association which promotes principles and strategies for public libraries.

In NAPLE Sister Libraries more than 70 public libraries from 12 European countries participate which cooperate with one or more libraries from another country.

Ljubljana City Library cooperates with County Public library from Kaunas (Lithuania) and Regional Public Library from Cracow (Poland).

Collaborating libraries have chosen the 13th of September as the NAPLE Sister Libraries Day.