The purpose of the study is to describe the microtoponymy of the Ulyanovsk Trans-Volga region. This territory includes the left-bank part of the modern Ulyanovsk region, that is, the land between the Kuibyshev reservoir and the Bolshoi Cheremshan river. The microtoponyms are analyzed in terms of their etymology. The material for this work was extracted from records of interviews with dialect speakers from the villages of the left-bank districts in the Ulyanovsk region. We have identified different types of place names in each thematic group. The names can be motivated by appellative vocabulary, anthroponyms, natural objects as well as appellatives. Most of the microtoponyms of the Ulyanovsk Trans-Volga region have Russian etymology. In this group of toponyms, there are not lots of substrate units. There are many more borrowings among the names of large rivers in this polyethnic region. However, even among the microtoponyms we can find the results of language contacts. First of all, we can point out borrowings from Turkic languages. These are such examples, as Kaibela, Kurd-yum, Chertany, Caraculy. Among the microtoponyms we also find loanwords of Finno-Ugric origin. These are mainly borrowings from the Mordovian languages: Pesha, Pochkarikha, Kurmysh, Mary, Kokshay. Some loaned toponyms were transformed on the Russian basis and framed with Russian formants.