Background and Objectives: This article presents an extended biography of Konstantin Aleksandrovich Leontiev (1889–1932), professor, head of the Physics Department, and director of the Physics Institute (1921–1932) at N. G. Chernyshevsky Saratov State University. Materials and Methods: The study draws upon a comprehensive range of archival sources, Leontiev’s scientific and educational publications, and contemporary memoirs. Results: K. A. Leontiev belonged to the prominent Russian scientific school of physics led by Moscow University professors P. N. Lebedev and P. P. Lazarev. As a talented 1911 graduate of the Physics and Mathematics Department of Moscow University, he joined the faculty of Saratov University in 1918. There, he conducted fruitful research, educational, organizational, and public outreach initiatives, and established a pioneering scientific and educational radio engineering laboratory. In the summer of 1928, Leontiev spearheaded the organizational efforts for the final meeting of the 6th Congress of the Russian Association of Physicists at Saratov University, an event that featured broad international participation. His major scientific and technical achievements include foundational works in radiophysics, thermodynamics, and acoustics (specifically, sound diffraction), as well as the development of the first broadcast radiotelephone station in Saratov. Conclusion: The historical data presented in this article provide a deeper and more comprehensive understanding of Professor K. A. Leontiev as a first-class research physicist and educator whose legacy laid the foundation for the radiophysics scientific schools at Saratov State University.