Russian oligarchs (Russian: олигархи, tr. oligarkhi) are business oligarchs of the former Soviet republics who rapidly accumulated wealth in the 1990s via the Russian privatisation that followed the dissolution of the Soviet Union. The failing Soviet state left the ownership of state assets contested, which allowed for informal deals with former USSR officials (mostly in Russia and Ukraine) as a means to acquire state property. Historian Edward L. Keenan has compared these oligarchs to the system of powerful boyars that emerged in late-medieval Muscovy.

The Russian oligarchs emerged as business entrepreneurs under Mikhail Gorbachev (General Secretary 1985–1991) during his period of market liberalization. Boris Berezovsky, a mathematician and formerly a researcher, became the first well-known Russian business oligarch.

Oligarchs became increasingly influential in Russian politics during Yeltsin's presidency (1991–1999); they helped finance his re-election in 1996. Well-connected oligarchs like Roman Abramovich, Michail Khodorkovsky, Boris Berezovsky and Vladimir Potanin acquired key assets at a fraction of the value at the loans for shares scheme auctions conducted in the run-up to the election. Defenders of the out-of-favor oligarchs argue that the companies they acquired were not highly valued at the time because they still ran on Soviet principles, with non-existent stock control, huge payrolls, no financial reporting and scant regard for profit.

Since 2014, hundreds of Russian oligarchs and their companies have been hit by the US sanctions for their support of "the Russian government's malign activity around the globe". In 2022, many Russian oligarchs were targeted and sanctioned by countries around the world as a rebuke of Russia's war against Ukraine.