Genius is a symbolic concept of modern European philosophy, which received special understanding in Russia at the turn of the 19th century. It is generally accepted that the borrowing genius appeared in Russian in the mid-18th century and finally became established in linguistic practice at the beginning of the 19th century. Meanwhile, the recording of the foreign-language lexeme and its variants in dictionaries published in Russia in the 18th century is on the periphery of scientific description. This determined the relevance of the study, which aims to demonstrate the presence of the lexeme genius in the Russian language and outline the semantic boundaries of this lexeme through reference to Russian dictionary editions of the 18th century. Continuous sampling, statistical, descriptive and comparative methods were used. Russian lexicographic editions of the 18th century were used as research material: explanatory dictionaries, dictionaries of foreign words, encyclopedic dictionaries, bi- and multilingual dictionaries, lexicons in educational publications. Overall, 52 dictionary editions were analyzed (reprints are not included in this number; but their materials were taken into account in the lexicographic analysis). The search was aimed at identifying not only dictionary entries for the lexeme genius, but also the functioning of this lexeme outside of lexicographic sections (for example, in the attached anthologies). The conducted research has shown that geniy/genius and foreign-language variants (Latin genius; French genie; German, Dutch Genius) are found in 18 dictionary editions, including those published at the very beginning of the 18th century. The Russified form geniy exceeds the transliterated form genius in frequency as a word-equivalent in the explanatory part of dictionary entries. From the point of view of chronology, the forms genius and geniy are fairly evenly represented in dictionaries both as capital words and as equivalent words. The use of the borrowing geniy goes beyond dictionaries and is observed in illustrative and explanatory texts. The semantic completeness of the lexeme reflects a combination (often bordering on fusion) of the ancient and modern European traditions. It is concluded that the dictionary corpus of the 18th century demonstrates the organic assimilation by the Russian language culture of a complex philosophical concept, which became a national lexical norm by the beginning of the 19th century.