The Moscow Kremlin (Russian: Московский Кремль) is the best known Kremlin (Russian citadel, for the etymology see Vasmer online). It is a historical fortified complex overlooking the Red Square in Moscow, which includes Kremlin Palaces, Kremlin Cathedrals, and the enclosing Kremlin Wall with Kremlin towers. The complex serves as the official residence and principal workplace of the President of the Russian Federation.

The site originates from the first settlements in the area on Borovitsky Hill where the Neglinnaya River flowed into the Moskva River. From the 11th century there was a significant fortified structure on the hill. The city was greatly extended by Prince Yuri Dolgoruky in the 12th century.  The fortress was named the Kremlin in 1331. Between 1366-1368, during the rule of Dmitri Donskoi, a white-stone citadel was constructed. By the 15th century the principalities of Russia were united under Grand Prince Ivan III Moscow, who became the Grand Prince of All Russia. He organised the reconstruction of the Kremlin, inviting a number of noted builders from Italy, the architect Aristotile Fioravanti among them.

The irregular triangle of the Kremlin wall encloses an area of 275,000 square metres (68 acres). Overall length of walls - 2235 metres (2444 yards), height from 5 to 19 m, thickness from 3.5 to 6.5 m. Existing walls  and towers were built in 1485 - 95. There are 20 Kremlin towers on the walls. 3 towers have circular section, the rest have square section. The highest tower (Spasskaya) is 71 m in height.

Cathedral Square is the heart of the Kremlin. It is surrounded by six buildings, including three cathedrals.
The Cathedral of the Dormition was completed in 1479 to be the main church of Moscow and where all the Tsars were crowned. The massive limestone facade, capped with its five golden cupolas was the design of Fioravanti. The gilded, three-domed Cathedral of the Annunciation was completed next in  1489, only to be reconstructed to a nine-domed design a century later. On the south-east of the square is the Cathedral of the Archangel Michael (1508), where over fifty members of the Russian Royal families are interred.

There are two domestic churches of the Metropolitans and Patriarchs of Moscow, the Cathedral of the Twelve Apostles (1653-56) and the one-domed exquisite church of the Deposition of the Virgin’s Robe, built by Pskov artisans over the years 1484-88 and featuring superb icons and frescoes from 1627 and 1644. The Saviour Cathedral in the Woods, dating back to the 1330s, and the 16th-century magnificent cathedrals of the Chudov Monastery and  the Ascension Convent were demolished in the 1930s to make room for the Communist Palace of Congresses. The current director of the Kremlin Museums, Elena Gagarina (Yuri Gagarin`s daughter) advocates a full-scale restoration of destroyed cloisters.

The other notable structure is the Ivan the Great Bell Tower on the north-east corner of the square, it is 81 m (266 ft) high and is said to mark the exact centre of Moscow. Its 21 bells would sound the alarm if any enemy was approaching.

The oldest secular structure still standing is the Palace of Facets (1491), which holds the imperial thrones, it was commissioned by Ivan III (the Great). Next oldest is the first home of the royal family, the Terem Palace. The original Terem Palace was commissioned by Ivan III, but most of the existing palace was built in the 17th century. The Terem Palace and the Palace of Facets are linked by the Grand Kremlin Palace. This was commissioned by Nicholas I in 1838. It was the largest structure in the Kremlin and cost 11 million rubles to build. It contains  luxurious reception halls, a ceremonial red staircase, private apartments of the tsars, and the lower storey of the Resurrection of the Lazarus church (1393), which is the oldest extant structure in the Kremlin and the whole of Moscow.

The Northeast corner of the Kremlin is occupied by the Arsenal, which was originally built for Peter the Great in 1701. The current Arsenal was built in 1817 after Napoleon`s troops destroyed the previous building in his failed invasion of Russia in 1812. The northwestern section of the Kremlin holds the Armoury building. Built in 1851 to a design by Konstantin Thon, it is currently a museum housing Russian state regalia and Diamond fund.

The name Kremlin is often used to refer to the government of the Soviet Union (1922-1991) and its highest members (such as general secretaries, premiers, presidents, ministers, and commissars), in the same way the name Westminster refers to the British government, or White House refers to the government of the United States. To some extent, it is still used in reference to the government of the Russian Federation. "Kremlinology" referred to the study of Soviet policies.

The name Kremlin is often used to refer to the government of the Soviet Union (1922-1991) and its highest members (such as general secretaries, premiers, presidents, ministers, and commissars), in the same way the name Westminster refers to the British government, or White House refers to the government of the United States. To some extent, it is still used in reference to the government of the Russian Federation. "Kremlinology" referred to the study of Soviet policies.