A raion (Ukrainian: район, romanized: raion; pl. райони, raiony), often translated as district, is the second-level administrative division in Ukraine. Raions were created in a 1922 administrative reform of the Soviet Union, to which Ukraine, as the Ukrainian Soviet Socialist Republic, belonged.

On 17 July 2020, the Verkhovna Rada (Ukraine's parliament) approved an administrative reform to merge most of the 490 raions, along with the "cities of regional significance", which were previously outside the raions, into just 136 reformed raions. Most tasks of the raions (education, healthcare, sport facilities, culture, and social welfare) were taken over by new hromadas, the subdivisions of raions. The 136 new districts include ten in Crimea, which have been de facto outside Ukrainian control since the start of the Russo-Ukrainian War in 2014.

Some cities of oblast significance, along with the two cities of national significance (Kyiv and Sevastopol), are also divided in city raions, also called urban raions. City raions have their own local administration and are subordinated directly to a city. They may contain other cities, towns, and villages.

On 17 July 2020, the number of raions in Ukraine was reduced to 136 (incl. 10 in Crimea) from the previous 490.

Note: the Russian Republic of Crimea continues to use the same administrative divisions. Raions located in the occupied Donbas territories (see below in grey) are currently only de jure.

Excluding the Autonomous Republic of Crimea.

In 2014, the Autonomous Republic of Crimea was annexed by Russia as the Republic of Crimea.

The populations in the table are from the census of 2001.^{[needs update]}