Turkmenistan is a republic in the south-western portion of Central Asia, bordered on the north by Kazakhstan and Uzbekistan, on the east by Uzbekistan and Afghanistan, on the south by Afghanistan and Iran, and on the west by the Caspian Sea. Ashgabat is Turkmenistan's capital and largest city. In Turkmen, the official language, the name of the republic is Turkmenistan Respublikasy (Republic of Turkmenistan). Turkmens constitute the dominant ethnic group. Turkmenistan was formerly the Turkmen Soviet Socialist Republic (SSR) of the Union of Soviet Socialist Republics (USSR). It became an independent country in 1991 and adopted its first post-Soviet constitution in 1992.