The Oskil or Oskol (Ukrainian: Оскiл; Russian: Оскол) is a south-flowing river in Russia and Ukraine. It arises roughly between Kursk and Voronezh and flows south to join the Siverskyi Donets which flows southeast to join the Don. It is 472 kilometres (293 mi) long, with a drainage basin of 14,800 square kilometres (5,700 sq mi).

The river has its sources on the Central Russian Upland, and flows through Kursk and Belgorod Oblasts in Russia, and through the eastern part of Kharkiv Oblast in Ukraine, where it joins the Seversky Donets river. An artificial lake, the Oskil Reservoir, was created in 1958 to help with flood protection and as a source of electricity.

There are several towns along the Oskil: Stary Oskol, Novy Oskol and Valuyki in Russia, and Kupiansk, Kupiansk-Vuzlovyi, Kivsharivka, Borova and Dvorichna in Ukraine.

On March 31, 2022, during the Russian invasion of Ukraine, the dam of the Oskil Reservoir was destroyed. In September of 2022, to resist the 2022 Ukrainian Kharkiv counteroffensive, Russian forces unsuccessfully used the Oskil River as a defensive barrier.