ENThe aim of this article is to discuss the formation of toponyms derived from ethnonyms in the southern part of Lithuania, known as Southern Aukštaitija (‘Southern Highlands’). This semantic group of toponyms differs from base words in both characteristic and meaning. The research of ethnonymic-origin toponyms reveals the ways in which proper names reflect the worldview of the inhabitants of the region. The material for the article was collected from the Geoinformation Database of Lithuanian Toponyms. To explain the origin of toponyms with reference to base words, the Dictionary of Lithuanian Surnames and the Dictionary of the Lithuanian Language were used. This research focuses on word formation based on the structural-grammatical classification of hydronyms developed by Lithuanian linguist and etymologist Aleksandras Vanagas. Each group of ethnonymic-origin toponyms studied is divided into primary and secondary toponyms, with the latter category split further into derivatives, composites, and compounds. Keywords: ethnonym, toponym, primary and secondary toponym of ethnonymic origin. [From the publication]