Tatyana Borisovna Yumasheva (Russian: Татьяна Борисовна Юмашева; born January 17, 1960; former also Dyachenko, née Yeltsina) is the younger daughter of former Russian President Boris Yeltsin and Naina Yeltsina.
She graduated from MSU Faculty of Computational Mathematics and Cybernetics in 1983. She then worked at the Salyut Design Bureau and later at Khrunichev State Research and Production Space Center until 1994.
Yeltsin made her his personal advisor in 1996 when his re-election campaign was faltering. A memoir written by Yeltsin, as reported by the New York Times  credited her with advising against “banning Communist Party, dissolving Parliament and postponing presidential elections” in 1996. She was particularly influential as Yeltsin recovered from heart surgery in late 1996. She became the keystone in a small group of advisors known as “The Family,” although the others (Alexander Voloshin and Valentin Yumashev) were not Yeltsin relatives.Boris Berezovsky and other oligarchs were often included in the group as well.
In 2000, Dyachenko’s name came up during a corruption investigation, but no charges were brought. Dyachenko remained on the staff of Yeltsin’s hand-picked successor Vladimir Putin, and was a key adviser to him during his 2000 election campaign, but Putin dismissed her later that year.
Dyachenko is portrayed in the 2003 satirical comedy Spinning Boris, based on the real experiences of U.S. political consultants in the 1996 campaign.
Dyachenko and Yumashev provided editorial assistance in preparing the last volume of her father’s memoirs, Midnight Diaries.
Dyachenko was married to Alexey Dyachenko, a businessman who was recently[when?] made CEO of Urals Energy, a company under investigation by the Putin government as of 2008. In 2001, Tatyana married her fellow presidential adviser Valentin Yumashev, and flew to London to have a baby. Until 2018 Yumashev was the father-in-law of oligarch Oleg Deripaska. Tatyana is a close friend of another multi-billionaire, Roman Abramovich.
It was reported that she along with her husband and their daughter have been citizens of Austria since 2009.