(until 1723, Kronslot), a city and port in Leningrad Oblast, RSFSR. Under the jurisdiction of the Leningrad city soviet. Situated on Kotlin Island in the eastern part of the Gulf of Finland, 29 km west of Leningrad. Population, 39,000 (1970). Founded in 1703 to protect the approaches to St. Petersburg, the original fortress was put into use on May 18, 1704.

Kronstadt became the main base for the Baltic Fleet in the 1720’s. On a number of occasions the city repulsed the attempts of enemy fleets to break through to the eastern part of the Gulf of Finland. It was very important in the training of personnel for the Russian fleet. Naval commanders, including Admirals G. A. Spiridov, F. F. Ushakov, D. N. Seniavin, M. P. Lazarev, P. S. Nakhimov, V. A. Kornilov, G. I. Butakov, and S. O. Makarov, and navigators (for example, I. F. Kruzenshtern, lu. F. Lisianskii, F. Bellingshausen, V. M. Golovnin, and F. P. Litke) served at Kronstadt.

Important revolutionary events took place in the city, including the Kronstadt uprisings of 1905 and 1906. In October 1917, by order of the Military Revolutionary Committee and the Central Committee of the Baltic Fleet (Tsentrobalt), the Kronstadt forces sent ships and detachments of sailors to Petrograd, where they participated actively in the October Armed Uprising. Later, they fought in the Civil War of 1918–20. A. G. Zhelezniakov, N. F. Izmailov, N. G. Markin, P. A. Pozharov, I. D. Sladkov, T. I. Ul’iantsev, P. D. Khokhriakov, and thousands of agitators and fighters for Soviet power came from the ranks of the Kronstadt sailors. In March 1921 an anti-Soviet rebellion took place in Kronstadt.

During the Great Patriotic War (1941–45) forces of the Baltic Fleet based in Kronstadt took part in the defense of Tallinn, Hango, and the Muhu archipelago. With its ship and coastal artillery, the city’s fortified sector was a vital part of the forces that took part in the heroic defense of Leningrad between 1941 and 1943 and in the rout of the German fascist troops in 1944. In 1954, in commemoration of the 250th anniversary of its founding, Kronstadt was awarded the Order of the Red Banner for its services in defense of the sea approaches to Leningrad.

Clothing is produced in Kronstadt, and there is a dairy plant and other enterprises. The General Technical Department of the Northwestern Correspondence Course Polytechnic Institute is located in the city, as are the Naval Museum and the A. S. Popov Study-Museum.

In the city, which has retained a regular layout dating from the Petrine period, there are a number of interesting examples of the residential architecture of the first quarter of the 18th century. The numerous examples of classicism include the biscuit bakery (1795–97, architect V. I. Bazhenov) and the barracks (1786–88, architect M. N. Vetoshnikov). The city is dominated by the Naval Cathedral (1903–13, architect V. A. Kosiakov). There are bronze monuments to Peter I (1841, P. P. Zhako) and Admiral Makarov (1913, L. V. Shervud).