Alexander Ivanovich von Hagen was a St. Petersburg architect of the Art Nouveau era, an academician and a full member of the Imperial Academy of Arts, as well as a state councilor. Among his significant projects are the city mosque, the Suvorov Museum, the building of the Nikolayev Academy, and the Kshesinskaya mansion.

Alexander Ivanovich was born in 1856 in Arkhangelsk into the family of the nobleman Johann von Hagen, who worked at the local branch of the State Bank. In 1875, he graduated from the Arkhangelsk gymnasium and entered the Academy of Arts, where he began practicing just two years later. From 1883 to 1887, he worked as an assistant to architects Pavel Yuryevich Syuzor, Alexander Fyodorovich Krasovsky, and Ivan Semyonovich Bogomolov.

In 1883, after graduating from the academy, von Hagen became an architect at the Sestroretsk Instrument Factory. From 1890, he taught at the Central School of Technical Drawing of Baron Stieglitz, the Nikolayev Engineering Academy, and the Institute of Civil Engineers. In 1895, for his project of a building for judicial institutions, he became an academician of architecture, and from 1896, a full member of the Academy of Arts.

From 1893 to 1906, von Hagen held the position of architect to Grand Duke Vladimir Alexandrovich, and from 1903, he also became the architect of the imperial court. He was part of the editorial board of the magazine "Zodchiy" and, at his initiative, the Society of Architect Artists was established.

In the last years of his life, Alexander Ivanovich von Hagen did not work due to a severe kidney illness. He committed suicide in his apartment on Nevsky Prospect (house No. 136) on the evening of March 7, 1914. His gravestone at Smolensky Cemetery was destroyed in 1935.