ENErnestas Galvanauskas – politician, scientist and public figure – is a person little known to public opinion not only in Lithuania but also in Poland. However, Lithuanian historians and political scientists see him as one of the more influential politicians who contributed to the construction of the Lithuanian state, more than Prime Minister Augustinas Voldemaras or President Antanas Smetona. The revival of the Lithuanian state is inextricably linked with the person of E. Galvanauskas. He was involved in the process of modernization of Klaipeda, led to the development of Lithuanian economics, which he applied in practice to manage the country’s economy. The research objective of this article is an in-depth analysis of the diplomatic activities of E. Galvanauskas in relation to the Hymans plan while he was Prime Minister of the government and Minister of Foreign Affairs. The Polish literature on the subject lacks sources concerning the history of Lithuania and Lithuanian-Polish relations in the interwar period, especially in the context of E. Galvanauskas’ political activity. Keywords: Ernestas Galvanauskas, Polish-Lithuanian relations, League of Nations, Hymans plan.