A kremlin (Russian: кремль, tr. kreml; IPA: [ˈkrʲemlʲ], fortress), same root as in kremen (Russian: кремень, tr. kremen; IPA: [krʲɪˈmenʲ], flint) is a major fortified central complex found in historic Russian cities. This word is often used to refer to the best-known one, the Moscow Kremlin, or metonymically to the government that is based there. Outside Russia, the name Kremlin is sometimes mistakenly thought of as being Saint Basil's Cathedral because of its distinctive environment, although the cathedral is not a part of the Moscow Kremlin.

Russia's presidential administration is located in the Moscow Kremlin. During the Cold War, the government of the USSR was located in the Moscow Kremlin, but now the Russian government occupies a building outside it.