Alina Kabayeva, 31, announced yesterday that she was standing down early after seven years as an lawmaker for the ruling United Russia party, without saying why.
"Alina Maratovna has accepted the offer of our shareholders to chair the board of directors," National Media Group's spokeswoman Oksana Razumova told AFP using Kabayeva's patronymic.
National Media Group (NMG) was created in a 2008 merger that included the holdings of businessman Yury Kovalchuk, who is also chairman of Bank Rossiya.
Brussels said in July that NMG "controls television stations which actively support the Russian government's policies of destabilisation of Ukraine".
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Kabayeva will replace Kovalchuk's nephew Kirill as head of the group.
NMG holds controlling stakes in Ren TV and Channel 5 as well as popular dailies Izvestia and Tvoi Den and the radio station Russkaya Sluzhba Novostei.
It also owns a share in Channel One television, one of Russia's most watched channels, and in Art Pictures studio, run by film director Fyodor Bondarchuk.
"She has no other experience in the media business," Vedomosti business daily said.
In 2008, Russian newspaper Moskovsky Korrespondent alleged that Putin had secretly divorced and was about to marry Kabayeva.
Both parties angrily denied the claim, with Putin lashing out at journalists for prying into his private life with "snotty noses and erotic fantasies". The newspaper announced its closure shortly afterwards.
The rumour has refused to die, however, and speculation over Putin's love life reignited after he and his wife Lyudmila announced their divorce last year.
She took part in the spectacular opening ceremony of the Sochi Winter Olympics in February.