Darya Klishina will be Russia's sole athletics competitor at the 2016 Olympics after the Court of Arbitration for Sport ruled she was eligible to take part.
The International Association of Athletics Federations dramatically suspended the 25-year-old long jumper's eligibility on Friday, having previously said she was the only one of Russia's 68-strong team that had a credible anti-doping record.
According to her lawyer, Paul Greene, the IAAF claimed three anti-doping samples she gave before and during the 2013 World Championships in Moscow showed evidence of being opened and then resealed.
This method of manipulating drug tests was identified in last month's explosive report into Russia's state-run doping programme by Canadian law professor Richard McLaren.
But in a decision released in the early hours of this morning local time in Rio, CAS upheld Klishina's appeal and said she could compete.
"At 1:00am today, the parties were informed that the application was upheld and that the athlete remained eligible to compete in the Olympic Games in Rio," the statement said.
"The CAS Panel applied the IAAF competition rules to conclude that the previous decision of the IAAF DRB (Doping Review Board), that the athlete complied with the relevant criteria because of her permanent residence outside Russia, still applied despite the additional information provided by Prof. McLaren.
"Relevantly, the athlete established that she was subject to fully compliant drug-testing in - and out-of-competition outside of Russia for the 'relevant period'."
Klishina has been based in the US since 2012. The two-time European indoor champion and gold medallist at the 2013 World Student Games in Kazan moved to Florida after signing a contract with global sports agency IMG.
The IAAF banned Russia's athletics federation last November after an earlier WADA-sponsored investigation revealed widespread cheating in the country's track and field programme.
Klishina, who also has a budding modelling career, has kept a low profile in recent weeks after she received personal abuse via social media from Russians who considered her to be a "traitor" for going to the Games.
The women's long jump competition will start on Tuesday evening.