George Papadopoulos, a former aide to then Republican candidate Donald Trump's 2016 campaign, has been sentenced to 14 days in prison.
He had pleaded guilty last year to lying to federal agents investigating whether campaign members coordinated with Russia before the election.
Prosecutors for special counsel Robert Mueller said Papadopoulos lied to agents about his contacts with Russians during the campaign "to minimise both his own role as a witness and the extent of the campaign's knowledge of his contacts."
Among those contacts were London-based professor Joseph Mifsud, who told him the Russians had "dirt" on Trump's Democratic presidential rival Hillary Clinton in the form of "thousands of emails."
Russia has denied US allegations that it interfered in the campaign and President Trump denies campaign collusion.
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Prosecutors had asked the judge to impose a prison sentence of up to six months, saying that Papadopoulos' lies impeded their investigation and that he did not cooperate.
In addition to the prison time, Papadopoulos was sentenced to one year of supervised release and 200 hours of community service and ordered to pay a fine of $US9,500.
"I hope to have a second chance to redeem myself," Papadopoulos told the judge. "I made a dreadful mistake but I am a good man," he said.
He and his wife left the courthouse without speaking to the press. However, Papadopoulos' mother Kiki told reporters she was satisfied he had received a fair sentence.
The White House distanced itself from Papadopoulos, referring to his campaign role as nothing more than a low-level coffee boy, after his guilty plea.
The sentence drew a quick response from Donald Trump on Twitter, as he scoffed at the two weeks of prison time by comparing it to an unverified cost figure for the Mueller probe.
"14 days for $28 MILLION - $2 MILLION a day, No Collusion. A great day for America!" the president tweeted.
During Friday's hearing, Papadopoulos' attorney Thomas Breen went out his way to praise the FBI, and also criticised Trump for calling the Russia probe "fake news" and "a witch hunt".
"The president of the United States hindered this investigation more than George Papadopoulos ever could," Breen told the judge.
He portrayed Papadopoulos as a naive young man who was "being worked by a pro," a reference to Professor Mifsud, whom he later said he believes was working for Russia and trying to take advantage of his client.
"No offence, but he was unsophisticated, he was naive and he was foolish," Breen said in court.
Papadopoulos was pictured in March 2016 sitting at a table with Trump, then-campaign adviser Jeff Sessions who went on to become US attorney general, and other foreign policy campaign advisers.
At that meeting, Papadopoulos proposed brokering a meeting between Trump and Russian President Vladimir Putin.
Sessions has previously testified to Congress that he pushed back against the proposal, but the memo filed by Papadopoulos's lawyers contradicts Sessions' account, saying that both Trump and Sessions appeared receptive to the idea.
