Flynn said in a statement that he is now "working to set things right.
"My guilty plea and agreement to cooperate with the Special Counsel's Office reflect a decision I made in the best interests of my family and of our country. I accept full responsibility for my actions," he said.
Court documents posted online show the investigation being led by Special Counsel Robert Mueller charged Flynn with one count of "willfully and knowingly" making false statements about his contacts with Russia's former U.S. envoy, Sergey Kislyak, during the transition in American administrations.
Mueller is probing allegations Russia sought to interfere in last year's presidential race through what U.S. intelligence agencies have termed an "influence campaign", and whether the Trump campaign cooperated with the effort.
Trump has staunchly denied any cooperation took place, and his lawyer distanced the president from Flynn in a statement that called the former national security adviser "a former Obama administration official" while noting Flynn served in the Trump administration for only 25 days.
"The false statements involved mirror the false statements to White House officials which resulted in his resignation in February of this year. Nothing about the guilty plea or the charge implicates anyone other than Mr. Flynn," Ty Cobb said.
Flynn left the administration in disgrace shortly after assuming his senior post amid disclosures he lied to officials, including Vice President Mike Pence, about his contacts with Kislyak and was a major Trump supporter during the campaign.
He is the fourth person charged in Mueller's investigation.
US: Flynn pleads guilty to lying to FBI
02 December 2017
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President Donald Trump's former National Security Adviser Michael Flynn pleaded guilty Friday after being charged with lying to the FBI.
