A raion (also spelt rayon) is a type of administrative unit of several post-Soviet states.
After the fall of the Soviet Union, some of the republics kept the raion (e.g. Azerbaijan, Belarus, Ukraine, Russia, Moldova, Kazakhstan, Kyrgyzstan) while others dropped it (e.g. Georgia, Uzbekistan, Estonia, Latvia, Armenia, Tajikistan, Turkmenistan).
It was started in 1923 in the Urals, North Caucasus, and Siberia as a part of the Soviet administrative reform and continued through 1929, by which time the majority of the country's territory was divided into raions instead of the old volosts and uyezds.
After the dissolution of the Soviet Union, raions as administrative units continue to be used in Azerbaijan, Belarus, Moldova, Russia, and Ukraine.
In Belarus, raions (Belarusian: раён, rajon[6]) are administrative units subordinated to oblasts.
In Ukraine, there are a total of 136 raions which are the administrative divisions of oblasts (provinces) and the Autonomous Republic of Crimea.