He is seen (circled) with a group of fellow military graduates in Chechnya.
British officials said the two were poisoned with Novichok, a military-grade chemical weapon that was developed in the Soviet Union, and blamed Russian President Vladimir Putin's government for the attack.
The website's claims have been dismissed by the Russian Foreign Ministry.
Bellingcat says its finding "starkly contradicts both this man's statements, as made in a TV interview to Russia's state-run RT network, and President Vladimir Putin's assertions that the person in question is merely a civilian named Ruslan Boshirov".
The 39-year-old GRU military intelligence service colonel is a married father-of-one. Britain has said the attack received approval "at a senior level of the Russian state", an accusation Moscow has fiercely denied.
"It was long enough for Reuters to quote it in a report, however, running under the headline: "'True identity' of Salisbury suspect revealed, United Kingdom defense minister says".
There was no immediate comment from Moscow on Bellingcat's latest claim. The BBC understands there is no dispute over the identification.
What information did we have before?
FILE PHOTO: Ruslan Boshirov, who was formally accused of attempting to murder former Russian intelligence officer Sergei Skripal and his daughter Yulia in Salisbury, is seen in an image handed out by the Metropolitan Police in London, Britain September 5, 2018.
Trump’s tariffs on $200 B of Chinese imports kick in
China will "earnestly reduce taxes and burdens for companies and strive to optimise the business environment", he added. The US buys far more from China than it sells to them, so China only has limited room to retaliate through trade.
On September 14, Bellingcat said it had reviewed Russian documents that indicated the two men had no records in the Russian resident database prior to 2009, a sign they may be working as operatives for the government.
He and the other suspect in the case, now still known as Alexander Petrov, were captured on CCTV in Salisbury on the day before and the day of the poisoning of the Skripals in March.
The Skripals were found unconscious on March 4 on a bench in Salisbury.
They denied any involvement in the poisoning.
In response to the Skripal poisoning, U.S. Ambassador to the U.K. Woody Johnson said in a tweet earlier this month that the U.S. and Britain "stand firmly together in holding Russian Federation accountable for its act of aggression".
What about the other suspect?
Bellingcat said the name was a "fake cover persona" for an as yet unidentified Russian individual. At age 18, he enrolled at a military school just 40 kilometers from his home, the Far-Eastern Military Command Academy in Blagoveschensk, one of Russia's elite training grounds for marine commandos and Spetsnaz officers.