Russia's appeal against its suspension by the International Olympic Committee (IOC) was dismissed by the Court of Arbitration for Sport (CAS) on Friday.
The IOC suspended the Russian Olympic Committee (ROC) in October last year for violating the territorial integrity of the membership of Ukraine by recognising illegally annexed territories.
After claiming his first world swimming title in Doha on Saturday, Ukrainian swimmer Vladyslav Bukhov said Russia should "absolutely not" be allowed at the Paris Olympics.
After the 21-year-old edged the two previous world champions to the wall to win the men's 50m freestyle, he said his preparation had been tough.
"It's hard, really hard," he said. "We train while Russian rockets are flying round the swimming pool. You never know if you stay alive or not. It's difficult. For all Ukrainians."
Asked if Russians should compete at the Paris Olympics in five months, he said: "Absolutely not."
"I want to say Russia is dangerous and should not be supported in competition."
IOL