A decision to ban Russian track and field athletes from Rio 2016 as a result of the country's alleged state-sponsored doping regime has been upheld by the Court of Arbitration for Sport.
Russia's athletics federation was suspended by the sport's world governing body, the IAAF, after an independent report found evidence of widespread doping.
The Russian Olympic Committee (ROC) and 68 athletes appealed against that decision but Cas has ruled the ban can stand after hearing evidence.
Separately, the International Olympic Committee (IOC) is considering calls to ban all Russian competitors across all sports from the Rio Games following a second report into state-sponsored doping.
"The Cas panel confirmed that the ROC is not entitled to nominate Russian track and field athletes to compete at the Rio 2016 Olympic Games considering that they are not eligible to participate under the IAAF competition rules," a spokesman said.
The IAAF said it was "pleased Cas has supported its position", saying the judgement had "created a level playing field for athletes".
IAAF president Lord Coe added: "This is not a day for triumphant statements. I didn't come into this sport to stop athletes from competing.
"Beyond Rio, the IAAF taskforce will continue to work with Russia to establish a clean safe environment for its athletes so that its federation and team can return to international recognition and competition."
The end of the road for Russia's athletes?
Despite the ban, the IAAF has said a handful of the country's athletes could compete in Rio as neutrals if they meet a number of criteria, including being repeatedly tested outside their homeland.
At least two Russian athletes - 800m runner and doping whistleblower Yuliya Stepanova and US-based long jumper Darya Klishina - have already taken advantage of that decision.
Now the Cas ruling has cleared the way for more to follow.
Cas said the ROC would still be able to nominate athletes to compete as neutrals at the Games. However, there appears to be little time for athletes to comply with the criteria given the Olympics start on 5 August.
Why were Russian athletes banned?
Russia was suspended from global track and field events by the IAAF in November 2015.
That followed the publication of an independent World Anti-Doping Agency (Wada) report that showed a culture of widespread, state-sponsored doping, with even the Russian secret service involved.
The country's sports minister, Vitaly Mutko, has since apologised for Russia's failure to catch cheating athletes but stopped short of admitting the scandal had been state-sponsored.
However, another Wada-commissioned report delivered earlier this week - the McLaren report - contained more damaging allegations and suggested senior figures in Russia's sports ministry were complicit in an organised cover-up.
The report implicated the majority of Olympic sports in the cover-up and claimed that secret service agents were involved in swapping positive urine samples for clean ones.
Following the McLaren report, the IOC faced calls to ban all Russian competitors from the 2016 Olympics.
It held an emergency meeting on Tuesday but said it would wait for Thursday's judgement from Cas before announcing any sanctions.
The IOC is expected to hold a second emergency meeting on Sunday.
How has Russia responded?
The Russian authorities have already suggested that they will look at ways to continue legal action.
Following the ruling, sports minister Mutko said Cas had set "a certain precedent" by punishing a collective group for doping offences by individuals.
Kremlin spokesman Dmitry Peskov added: "The principle of collective responsibility cannot be acceptable. The news is not very good."
London 2012 pole-vault gold medallist Yelena Isinbayeva - one of the 68 to appeal to Cas - said the ruling was "a blatant political order".
She told the Tass news agency: "Thank you all for this funeral for athletics."