The concept „libretto” is a diminutive form of the Italian word „libro”, that is, a book, and literally means a little book. This the name is due to the fact that opera librettos from the end of the 17th century were issued for theater visitors in the form of small books. Its first and main meaning is the complete literary text of an opera, operetta, a literary script for a ballet performance. This term is also sometimes used to refer to the text of major liturgical works, such as the Mass, requiem and sacred cantata. Structure of the libretto should be extremely laconic since the sung word lasts longer than the spoken word. The text of the libretto can be an original literary work, but most often the libretto is based on some kind of artistic primary source, written mainly in poetic language, but it can also be in prose, which has been allowed into opera in the last 150 years. Not every literary work can serve as a prototype for an opera libretto. First of all, it should have a sufficient degree of plot tension and a high measure of eventfulness, as well as the presence of vivid characters and entertaining scenes. It should be saturated with dialogues, which can later become vocal speech. But the playwright can rethink the idea of the original source in a new way, even if it will be fundamentally different from its original form. An in-depth study of libretto issues has shown that it has a fundamental meaning for opera and for its stage life. Considering that the libretto is an artistic text with a certain communicative task, that it has its own laws of plot construction and development, elaborated over the long history of the evolution of the opera genre, the libretto can be called a specific literary genre. By preserving and digitizing the entire legacy of opera librettos, we will do an invaluable service to future generations and make a great contribution to the further development of operatic art.