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The sanctions come eight years after the US sanctioned two of the men — Gennady Timchenko and Boris Rotenberg — and four years after the third, Igor Rotenberg, was also hit by sanctions.
Gennady Timchenko, 69, is a major shareholder in Bank Rossiya, which expanded its branches and investments in Ukraine after Russia’s 2014 annexation of Crimea.
The bank has been involved in forging transport links and travel cards that allow the public to travel easily around the Crimean Peninsula. The move has supported the “consolidation of Crimea into the Russian Federation”, UK officials say.
Mr Timchenko, a citizen of Russia, Finland and Armenia, graduated from with a degree in electrical engineering from an institute in St Petersburg and built his fortune in oil and gas. Forbes reported he is worth $23.5 billion, making him one of Russia’s richest men.
He was one of the founders of the Gunvor oil trading company but sold his stake to his partner a day before he was hit with US sanctions in 2014.
A passionate ice hockey fan, he heads the sport's professional league in Russia and is president of his home town team in St Petersburg. He owns jets and a 40-metre yacht, the M/S Lena, named after his wife.
Boris Rotenberg, 65, has close ties to Mr Putin forged in the gyms and on the judo mats where they trained during their youth. A former professional judo trainer, he often acted as Mr Putin’s sparring partner.
He is the co-owner with his older brother, Arkady, of SMP bank and SGM, the largest company dedicated to building gas pipelines and electrical power supply lines in Russia.
He is also the member of the St Petersburg Connection, a powerful energy lobby under the leadership of Mr Putin. Forbes estimates his wealth to be $1.2bn.
The US Treasury claimed that the president awarded the brothers contracts worth billions of dollars for contracts with Gazprom, the state-owned energy corporation, and for the Sochi Olympics in 2014 — the year they were sanctioned by the US government.
The US has described them then as “members of the Russian leadership's inner circle”. He holds Russian and Finnish citizenship.
The son of Arkady, Igor Rotenberg, 47, secured significant assets in the Russian energy sector from his father when he was sanctioned in 2014.
The elder Mr Rotenberg sold Igor 79 per cent of the Russian oil and gas drilling company Gazprom Burenie. His uncle, Boris, owns 16 per cent.
Igor has major investments in Russia’s transport sector — including toll collection systems for lorries — and continues to benefit from his family’s ties with Mr Putin. He was once a senior manager at state-owned Russian Railways.
Married with three children, he is said to be worth $1.1bn. Born in St Petersburg, he now lives in Moscow and is the only one of the three men who holds only Russian citizenship.