Boris Berezovsky, the exiled Russian oligarch and long-time opponent of the Kremlin, in London in 2007.
MOSCOW — Boris A. Berezovsky, once the richest and most powerful of the so-called oligarchs who dominated post-Soviet Russia, and a close ally of Boris N. Yeltsin who helped install Vladimir V. Putin as president but later exiled himself to London after a bitter falling-out with the Kremlin, died Saturday.
He was 67 and lived in London, where last year he lost what was billed as the world’s largest private lawsuit in history — an epic battle with another Russian oligarch, Roman A. Abramovich, in which legal and other costs rose to about $250 million.
Mr. Berezovsky’s death was first reported in a post on Facebook by his son-in-law, Egor Schuppe, and confirmed by a lawyer, Alexander Dobrovinsky, who said that Mr. Berezovsky may have committed suicide.
Recent news reports described how Mr. Berezovsky had begun to sell personal assets, including a yacht and a painting by Warhol, “Red Lenin,” to pay debts related to the lawsuit.
The lawsuit, in which Mr. Berezovsky had brought a $5.1 billion claim against Mr. Abramovich in a dispute over the sale of shares in the Russian oil company Sibneft and other assets, ended in a spectacular defeat.
In her ruling, the judge, Elizabeth Gloster, called Mr. Berezovsky, an “unimpressive and inherently unreliable witness” and at times a dishonest one. By contrast, the judge said Mr. Abramovich had been “a truthful, and on the whole, reliable witness.”
Mr. Berezovsky was a leading Soviet mathematician who after the fall of Communism went into business and figured out how to skim profits off what was then Russian’s largest state-owned carmaker. Along with spectacular wealth, he accumulated enormous political influence, becoming a close ally of Mr. Yeltsin’s.
With Mr. Yeltsin political career fading, Mr. Berezovsky helped engineer the rise of Mr. Putin, an obscure former K.G.B. agent and one-time aide to the mayor of St. Petersburg, who became president of Russia in 2000 and last May returned to the presidency for a third term.
After his election, Mr. Putin began a campaign of tax claims against a group of rich and powerful Russians, including Mr. Berezovsky and the oil tycoon Mikhail B. Khodorkovsky, who remains jailed in Russia.
Mr. Berezovsky fled to London, where he eventually won political asylum and at one point raised tensions by calling for a coup against Mr. Putin.
