The first person has been jailed as part of the FBI inquiry into alleged collusion between Donald Trump’s presidential campaign team and Russia.
Dutch lawyer Alex van der Zwaan, 33, was sentenced to 30 days in prison for lying to investigators about contacts with ex-Trump aide Rick Gates.
He struck a plea deal in February.
Van der Zwaan is the son-in-law of one of Russia’s richest men and was the 19th person to be charged by special counsel Robert Mueller.
The indictment against him did not refer to the 2016 election campaign. Mr Trump has not been accused of any wrongdoing.
In March, the US imposed sanctions on 19 Russians, including 13 people charged by Mr Mueller’s inquiry, over accusations of interference in the 2016 election and alleged cyber-attacks.
In court on Tuesday, Van der Zwaan was also fined $20,000 and sentenced to two months of supervised release.
The Dutchman is a London-based lawyer who formerly worked at international law firm Skadden, Arps, Slate, Meagher & Flom.
The firm, which is co-operating with the investigation and which fired him last year, worked with former Trump campaign chief Paul Manafort and his ex-colleague Mr Gates at a time when they were both political consultants in Ukraine.
Van der Zwaan, who speaks French and Russian and graduated from King’s College London in 2006, is married to the daughter of Russian billionaire German Khan.