The Ukrainian–Soviet War (Ukrainian: українсько-радянська війна, romanized: ukrainsko-radianska viina) is the term commonly used in post-Soviet Ukraine for the events taking place between 1917 and 1921, nowadays regarded essentially as a war between the Ukrainian People's Republic and the Bolsheviks (Russian SFSR and Ukrainian SSR). The war ensued soon after the October Revolution when Lenin dispatched Antonov's expeditionary group to Ukraine and Southern Russia.

Soviet historiography viewed the Bolshevik victory as the liberation of Ukraine from occupation by the armies of Western and Central Europe (including that of Poland). Conversely, modern Ukrainian historians consider it a failed war of independence by the Ukrainian People's Republic against the Bolsheviks. The conflict was complicated by the involvement of the Revolutionary Insurgent Army of Ukraine, non-Bolshevik Russians of the White Army, and the armies of the Second Polish Republic, Austria-Hungary, and the German Empire, among others.

In Soviet historiography and terminology, the armed conflict is depicted as part of the greater Russian Civil War: in Ukraine, this war was fought between the national government (led by Symon Petliura) and the Russian Bolshevik government (led by Lenin).

The war may be divided into three phases:

After the February Revolution of 1917, the nationalities within the Russian Republic (formerly the Russian Empire) demanded national autonomy from Petrograd. In the summer of 1917, the Russian Provisional Government approved regional administration over some parts of Ukraine.

In November 1917, the Central Council of Ukraine denounced the Bolsheviks' armed coup against the Russian Provisional Government, known as the October Revolution, and declared it would decisively fight against any attempted similar coup in Ukraine. A special joint committee for preservation of revolution was organized to keep the situation under control. The Kiev Military District command tried to prevent a Bolshevik coup, leading to street fights and eventually surrendering of pro-Bolshevik troops in the city. On November 14, 1917, the Ukrainian Central Rada issued its "Appeal of the Central Council to the citizens of Ukraine" in which it sanctioned transfer of the state power in Ukraine to itself. On November 16, a joint session of the Rada and executive committee of the local workers and soldiers soviets recognized the Central Rada as the regional authority in Ukraine. On November 20, 1917, the Rada declared Ukraine the Ukrainian People's Republic as an autonomous part of the Russian Republic and scheduled the January 9, 1918 elections to a Ukrainian Constituent Assembly. The Secretary of Military Affairs, Symon Petliura, expressed his intentions to unite both the Southwestern and Romanian fronts that were stretched across Ukraine into one Ukrainian Front under the command of Colonel General Dmitry Shcherbachev.

On December 17, 1917, the Russian Bolsheviks planned a rival All-Ukrainian Congress of Soviets and on December 11–12, 1917, they set off a number of coups across Ukraine in Kiev, Odessa and Vinnytsia. They were successfully defeated by the Rada. On December 17, 1917, Sovnarkom, which had initiated peace talks with Central Powers earlier that month, sent a 48-hour ultimatum to the Rada requesting it stop "counterrevolutionary actions" or prepare for war. Also on December 17, 1917, Reingold Berzins led his troops from Minsk towards Kharkov to the Don. They engaged in an armed conflict at a rail station in Bakhmach with the Ukrainian troops who refused to let the Russian red forces (three regiments and an artillery division) pass. The Central Rada did not accept the accusations and stated its conditions: recognition of the Ukrainian People's Republic, non-interference in its internal affairs and affairs of the newly organized Ukrainian Front, permission on transferring of Ukrainized troops to Ukraine, division of the former imperial finances, participation of the Ukrainian People's Republic in the general peace negotiations. The same day the All-Ukrainian Congress of Soviets in Kiev, after the Bolshevik delegation left, recognized the authority of the Ukrainian government and denounced the ultimatum of the Soviet Russian government. The Kiev Bolsheviks in their turn denounced that congress and scheduled another one in Kharkov. The next day, Sovnarkom in Moscow decided to go to war. Vladimir Antonov-Ovseyenko was appointed by Vladimir Lenin the commander-in-chief of expeditionary force against Kaledin and the South Russia, while near the borders with Ukraine (Bryansk–Belgorod), Red troops began to gather.

The Kievan Bolsheviks who fled to Kharkov joined the regional Congress of Soviets of the Donetsk-Krivoy Rog Soviet Republic. They then declared this meeting the First All-Ukrainian Congress of Soviets that announced the creation of the Ukrainian People's Republic of Soviets. It called the Central Rada of Ukraine an enemy of the people declaring war against it on January 2. The Rada then broke all ties with Petrograd on January 22, 1918, and declared independence, thereby commencing the Ukrainian War of Independence. It was around this point that Bolshevik troops began invading Ukraine from Russia. Russian military units from Kharkov, Moscow, Minsk and the Baltic Fleet invaded Ukraine.