Michael Cohen, the former lawyer to Donald Trump who once said he’d take a bullet for the president, has been given a 36-month prison sentence.
He is the first member of Mr Trump's inner circle to be jailed over the special counsel's inquiry into alleged Russian meddling in the 2016 election.
He has pleaded guilty to crimes including campaign finance violations, tax evasion and lying to Congress.
In a New York court on Wednesday Cohen lashed out at his former boss.
The 52-year-old told Judge William Pauley that Mr Trump caused him to "follow a path of darkness rather than light".
He told the court his "weakness was a blind loyalty to Donald Trump" and that he "felt it was my duty to cover up his dirty deeds".
The sentencing was related to two separate cases brought by the Southern District of New York and Special Counsel Robert Mueller's Russia investigation.
Mr Cohen pleaded guilty to campaign finance violations for his role in making hush money payments to women who alleged affairs with Mr Trump.
Mr Trump has acknowledged the payments despite denying the affairs, and called them a private transaction unrelated to his campaign.
He will serve that term concurrently with a two-month sentence he was given for lying to Congress about a possible Trump Tower project in Moscow, a charge levelled by Special Counsel Mueller.