Alexey Victorovich Shchusev (Russian: Алексей Викторович Щусев; 8 October [O.S. 26 September] 1873 – 24 May 1949) was a Russian and Soviet architect who was successful during three consecutive epochs of Russian architecture – Art Nouveau (broadly construed), Constructivism, and Stalinist architecture, being one of the few Russian architects to be celebrated under both the Romanovs and the communists, becoming the most decorated architect in terms of Stalin prizes awarded.

In the 1900s, Shchusev established himself as a church architect, and developed his proto-modernist style, which blended Art Nouveau with Russian Revival architecture. Immediately before and during World War I he designed and built railway stations for the von Meck family, notably the Kazansky Rail Terminal in Moscow. After the October Revolution, Shchusev pragmatically supported the Bolsheviks, and was rewarded with the contract for the Lenin Mausoleum. He consecutively designed and built three mausoleums, two temporary and one permanent, and supervised the latter's further expansion in the 1940s. In the 1920s and early 1930s he successfully embraced Constructivist architecture, but quickly reverted to historicism when the government deemed modernism inappropriate for the Communist state. He was one of the members of the art association 'The Four Arts', which existed in Moscow and Leningrad in 1924-1931.

His career proceeded smoothly until September 1937, when, after a brief public smear campaign, Shchusev lost all his executive positions and design contracts, and was effectively banished from architectural practice. Modern Russian historians of art agree that the charges of professional dishonesty, plagiarism, and exploitation raised against Shchusev were, for the most part, justified. In the following years he gradually returned to practice, and restored his public image as the patriarch of Stalinist architecture. The causes of his downfall and the forces behind his subsequent recovery remain unknown.

Alexey Shchusev was born in Kishinev in the Russian Empire (present-day Chișinău, Moldova) as the fourth of five children in the family of a provincial civil administrator. Both his parents died when Alexey was fifteen years old. With the help of older siblings and a scholarship from the Kishinev city council, Alexey and his younger brother Pavel (1880–1957) graduated from the local gymnasium and continued their educations at the university level. Pavel, like Alexey, would become an architect and a bridge engineer; he would collaborate with Alexey on bridge projects in Moscow and be the custodian of Alexey's artwork and archive after his death.

In 1891, Alexey left Kishinev and enrolled at the Imperial Academy of Arts in Saint Petersburg. In his first years at the Academy, Shchusev attended both architecture and painting classes. In 1894, he joined the class of Leon Benois and concentrated on architecture. At about the same time, 1893 or 1894, he designed and built his first tangible project on a private estate in Bessarabia. In 1895, he took his first study tour of Central Asia, with professor Nikolay Veselovsky. In the same year, Shchusev designed and built a crypt chapel in Russo-Byzantine style at the Alexander Nevsky Lavra. Later, according to Shchusev himself, he browsed through the obituaries in a newspaper, and was making cold calls to the families of the deceased. A family member accepted his offer, and Shchusev (still an undergraduate student) received his first commission in Saint Petersburg.

In 1896, his last year at the Imperial Academy, Shchusev studied old Northern Russian architecture in Kostroma, Rostov, and Yaroslavl; and the European architecture of Romania and Austria-Hungary. The next year, he graduated from the academy with the right to a state-sponsored tour of Europe. While the paperwork for the latter was being prepared, he traveled to Kishinev to marry his fiancée, Maria Karchevskaya. He spent the winter of 1897–1898 in Samarkand, with Veselovsky, studying and documenting medieval shrines. This exposure to Islamic architecture would influence his design of the 1898 orientalist Karchevsky House in Kishinev, and later designs for Soviet-era projects built in the Caucasus, Kazakhstan, and Central Asia. In August 1898, Shchusev and his wife started their sixteen-month Grand Tour, via Vienna, Trieste, Italy to Tunisia, and then via Italy to Paris, where Shchusev studied for six months at the Académie Julian.

Upon returning to Saint Petersburg, Shchusev tried to set up an independent practice, but failed to find clients. His fortunes changed in 1901–1902, when his design for a new iconostasis for the main cathedral of the Kiev Pechersk Lavra was noticed approvingly by fellow architects and the Orthodox clergy. He was appointed as a consultant to the Holy Synod, and soon had the chance to assist Mikhail Nesterov with the repairs to the poorly built church in Abastumani. Nesterov was impressed, and became Shchusev's patron. Shchusev's contracts with the Kharitonenko [ru] and von Meck families and the charity of Grand Duchess Elisabeth were, to varying degrees, the result of Nesterov's recommendations. In the course of a decade, Shchusev established himself as primarily a church architect, and quickly progressed from historic styles to the creation of his own proto-modernist style, blending Art Nouveau with the Russian Revival tradition. He did not have as much luck in getting lucrative residential and government contracts; his lay buildings of the period are scarce and, as a whole, are distinctly inferior to his churches. Shchusev's church murals, influenced by the works of Viktor Vasnetsov and Mikhail Vrubel, did not impress contemporary observers either. Alexander Blok complained that they were "neither bold, nor religious".

In 1904, the Holy Synod entrusted Shchusev with the restoration of the ruined twelfth century church [ru] in Ovruch. Shchusev's controversial five-domed design in the Byzantine style was much debated by architects and preservationists, but was nevertheless approved for construction in 1907. Further debate followed; and in 1908 Shchusev was forced to submit a revised design, with the help of Pyotr Pokryshkin [ru] and Leonid Vesnin. From 1908 to 1911, the church was rebuilt, according to the revised design.