Russian tycoon Mikhail Prokhorov, 46, has been elected to lead the pro-business Russian political party Right Cause.
Members of the party voted in the billionaire on Saturday.
Prokhorov is one of Russia's richest men and owns a U.S. professional basketball team. He heads the Onexim Group, an investment firm that has interests in mining, banking and other industries.
Prokhorov announced last month that he planned to lead the Right Cause Party in a campaign for December's parliamentary elections.
In a speech to party members Saturday, he set the goal of making Right Cause the number two party in parliament and then overtaking the ruling United Russia party to become number one. He said he does not want Right Cause to be described as "opposition," a word he said Russian citizens associate with "marginal groups" that have "lost touch with reality."
The Associated Press news agency says Right Cause is viewed as a Kremlin creation designed to attract opposition-minded voters, while creating an illusion of competition with the ruling party.
Prokhorov's election marks the first time a top businessman has entered Russian politics since oil magnate Mikhail Khodorkovsky was arrested in 2003 on charges he says were politically-motivated.
At the time of his arrest Khodorkovsky had been supporting politicians opposed to then-President Vladimir Putin. Khodorkovsky, once Russia's richest man, remains in prison after being convicted of tax fraud, money laundering and stealing from his former oil company, Yukos.
Last week, Russian media reported that tax inspectors in the Siberian city of Krasnoyarsk were suing Prokhorov for $70 million in allegedly unpaid taxes.
Officials told Russian media that Prokhorov is suspected of underpaying taxes owed to the Russian state on a transaction in Britain in 2008. Local tax inspectors have asked Russia's anti-monopoly service for help in pursuing the case against the tycoon.
Some information for this report was provided by AP, AFP and Reuters.