Alexander Grigoryevich Gagarin was born on December 22, 1855, in St. Petersburg. His father, Grigory Grigoryevich Gagarin, was a well-known amateur artist, court chamberlain, and vice-president of the Imperial Academy of Arts. His mother, Sofia Andreevna, née Dashkova, served as a lady-in-waiting to Empress Alexandra Fyodorovna and later became a lady of honor to Empress Maria Fyodorovna. Alexander was baptized on January 18, 1856, in the Court Cathedral, where the godmother was Empress Alexandra Fyodorovna. He began his education in a private boarding school and in 1869 entered the fourth grade of the Larin Gymnasium. After graduating in 1874, he enrolled in the Faculty of Physics and Mathematics at St. Petersburg University. After university, he served as a volunteer in the Guard Horse Artillery, then passed the officer exam and graduated with honors from the Mikhailovskaya Artillery Academy in 1884. On January 7, 1900, at the suggestion of Finance Minister S. Yu. Witte, Gagarin was appointed director of the new St. Petersburg Polytechnic Institute. In the early years, he worked on developing the institute's charter, organizing the educational process, and selecting the faculty. Thanks to his efforts, well-known scientists and educators such as Professors K. P. Boklevsky, I. A. Meshchersky, A. S. Posnikov, and others came to work at the institute. Alexander Grigoryevich Gagarin passed away on December 22, 1920, at the age of 65 after a complicated operation at the Pskov Hospital. He was buried at the cemetery of the Church of the Ascension in the village of Belskoye Ustye.