Boris Abramovich Berezovsky (Russian: Бори́с Абра́мович Березо́вский) (also known as Platon Elenin) (born January 23, 1946), is a Russian businessman, billionaire, a mathematician and a member of Russian Academy of Sciences. He is best known for his role as a Russian oligarch, media tycoon and prominent politician during the presidency of Boris Yeltsin in the 1990s. He has been described by critics as the epitome of Russian "robber capitalism", but he denies having ever taken part in the violence that tainted Russian business during that era. Berezovsky was at the height of his power in the later Yeltsin years, when he was deputy secretary of Russia's security council, a friend of Boris Yeltsin's daughter Tatyana Dyachenko, and a member of the Yeltsin inner circle, or "family".

Berezovsky made his fortune by capturing state assets at knockdown prices during Russia's rush towards privatisation. He took ownership of the Sibneft oil company and became the main shareholder in the country's main television channel, ORT, which he turned into a propaganda vehicle for Boris Yeltsin in the run-up to the 1996 presidential election. It is said that, in contrast to Russian entrepreneurs such as Vladimir Gusinsky, Berezovsky did not enrich any of the enterprises with which he became involved or took over (e.g. Sibneft, ORT, the car dealership Avtovaz, Omsk Oil Refinery, National Sports Fund, and aluminum smelters Bratsk, Krasnoyarsk, and Novokuznetsk), but instead drained them of cash. Although he helped Vladimir Putin enter the "family", and funded the party that formed Putin's parliamentary base, Putin moved to regain control of the ORT television station and to curb the political ambitions of Russia's oligarchs, who were extremely unpopular with the Russian public.

Following the ascent of Putin to the Russian presidency, Berezovsky went into opposition and fled the country after being accused of defrauding a regional government of US$13 million. He was later granted political asylum in the United Kingdom. He has since publicly stated that he is on a mission to bring down Putin "by force". In the UK, he became associated with Akhmed Zakayev, Alexander Litvinenko and Alex Goldfarb in what has become known as "the London Circle" of Russian exiles. He is a founder of International Foundation for Civil Liberties. According to Professor Richard Sakwa, Berezovsky's behaviour is always marked by audacity and cunning.