The intellectual history of the early Turkish Republic has not yet been sufficiently researched, particularly regarding the multifaceted language reform and the linguistic theories underlying it. The study demonstrates, following a presentation of the history of the language reform, that these theories—from the Sumerian-Turanian hypothesis to the sun language theory—primarily have their roots in European thought of the 19th and early 20th centuries. These ideas were adapted or transformed more or less arbitrarily from the Turkish side and remain a significant factor in contemporary Turkish intellectual life. The work also provides a detailed examination of the actual influence of the Viennese Orientalist H.F. Kvergic on the Turkish proto-language theory for the first time, and it investigates Atatürk's role in the language reform. The bibliographic section includes approximately 1,300 titles, thus representing a comprehensive collection of literature on the subject. The appendix offers, among other things, Turkish documents related to the language reform for the first time in German translation, which aims to facilitate the understanding of this important area of Turkey's cultural history for non-Turkologists.