The problem of the formation of the Grand Duchy of Lithuania is one of the most important in the history of Belarus. In this state, the formation of the Belarusian people took place. Nevertheless, for a long time the history of this state: its emergence, formation, heyday, struggle for the right to life and, finally, disappearance from the political map of Europe, was a taboo topic for Belarusian historians. Only with the independence of our country did Belarusian historical science have the opportunity to develop its own view of the heritage of this largest European power and determine the participation of the Belarusian ethnic group in it.