The L. V. Kochubey Mansion, also known as the Y. S. Nechaev-Maltsov Mansion, is a historic building in St. Petersburg. It was built in the 1840s by architects Roman Kuzmin and Harald Bosse for Prince Lev Kochubey. In 1883-1884, the building was reconstructed under the guidance of architect Leonty Benois for Yuri Nechaev-Maltsov. As of 2019, the building is state-owned and has been used by the Ministry of Internal Affairs of Russia since 1994.

In the early 19th century, the plot where the mansion later appeared belonged to Admiral Grigory Kushelev. There were wooden structures and a large garden on this territory. In the early 1840s, the admiral's son built a stone house, which was then rented by Count S. O. Berzhinsky. Later, the building passed to G. S. Stroganov, the great-grandson of Count A. S. Stroganov, president of the Imperial Academy of Arts.

In the 1840s, the plot on Sergievskaya Street (now Tchaikovsky Street) was acquired by Lev Kochubey, who reconstructed the mansion. The facades of the building, made of Pudost limestone, were designed in the style of Florentine Neo-Renaissance with characteristic windows, arches, and machicolations, as well as a prominent base and cornice. The interiors were decorated in the Baroque and Rococo styles with rich stucco and paintings.

In the early 1880s, the new owner became Yuri Nechaev-Maltsov. He invited Leonty Benois for another reconstruction of the building. Nechaev-Maltsov, possessing significant wealth and the rank of actual state councilor, sought to create a true palace for receiving high-ranking guests and the imperial family. Benois commissioned artist Heinrich Semiradsky to create a panel for the main hall, and a piano with paintings by Ernst Lipgart and Konstantin Makovsky was acquired for the ballroom. The house was adjacent to a winter garden with a fountain and a greenhouse with canaries and tropical birds. According to Nechaev-Maltsov, a palm tree in the greenhouse grew so large that the glass ceiling had to be raised twice.

After Yuri Nechaev-Maltsov's death in 1913, the mansion was inherited by his adopted son Elim Pavlovich Demidov San Donato, becoming the last owner of the building. After the revolution, the mansion was nationalized. In the 1920s, it was transferred to the Petrograd District Film Committee, and in 1933, to the Smolny District Executive Committee. From 1936 to 1994, the building was occupied by the Dzerzhinsky Executive Committee, and after the collapse of the USSR, by the district administration. In 1994, the mansion was transferred to the Central City Administration of the Ministry of Internal Affairs, and in 2014, to the Main Directorate of the Ministry of Internal Affairs for St. Petersburg and the Leningrad Region.