A jury has found the 77-year-old guilty after a high-profile trial. It comes just six months before he goes head to head with Joe Biden in a bid to return to the White House.
Donald Trump has become the first former US president to be criminally convicted.
In a historic decision, a New York jury has found him guilty of falsifying business records to commit election fraud.
The former president is set to be sentenced on 11 July - days before the start of the Republican National Convention on 15 July where Trump is expected to be formally nominated for president.
The verdicts plunge the country into unexplored territory ahead of the election on 5 November as opinion polls show Trump and Joe Biden locked in a tight race for the White House.
Trump faces a maximum sentence of four years in prison, though others convicted of the same crime often receive shorter sentences, fines or probation.
Speaking outside the court, Trump said the conviction was a "disgrace" and that he is "a very innocent man".
He said the trial was "rigged" and that the judge was "conflicted" and "should never have been allowed to try this case".
"This is long from over," Trump added.
After the conviction, he travelled in a convoy of black jeeps to dinner in New York City.
Meanwhile, a spokesperson for Joe Biden said in a statement: "No one is above the law."
"Donald Trump has always mistakenly believed he would never face consequences for breaking the law for his own personal gain," said Michael Tyler, the Biden-Harris campaign’s communications director.
"The threat Trump poses to our democracy has never been greater. He is running an increasingly unhinged campaign of revenge and retribution, pledging to be a dictator ’on day one’ and calling for our Constitution to be ’terminated’ so he can regain and keep power," he added.
"A second Trump term means chaos, ripping away Americans’ freedoms and fomenting political violence - and the American people will reject it this November."
Alvin Bragg, the New York district attorney who brought the case against Trump, said in a press conference after the verdicts that his team "followed the facts and the law without fear or favour".
He thanked the NYPD, court staff and the jury, saying the latter was "careful and attentive".
"I feel a deep gratitude to work alongside them to be a part of this system," he said.
"While this defendant may be unlike any other in American history, we arrived at this trial and ultimately today at this verdict, in the same manner as every other case," Mr Bragg added
Meanwhile, Michael Cohen, Trump’s former fixer and a key witness in the trial, said: "Today is an important day for accountability and the rule of law.
"While it has been a difficult journey for me and my family, the truth always matters."
He also posted on X celebrating the verdicts.
The case against Trump
Trump was at the centre of a scheme to cover up "hush money" payments to buy the silence of a porn star in the days before the 2016 election.
When revelations by Stormy Daniels of a sexual liaison with Trump threatened to upend his presidential campaign, he directed his lawyer to pay her $130,000 (£102,000) to keep her quiet.
The payment buried the story, and Trump was later elected to be the 45th president of the United States.
Trump watched the jurors dispassionately as they were polled to confirm the guilty verdict. They had deliberated for nine-and-a-half hours.
Judge Juan Merchan thanked the jurors for their service, saying: "Nobody can make you do anything you don’t want to do. The choice is yours." Jurors are now free to speak about the trial.
Both supporters and protesters gathered outside and could be heard in the hallway on the 15th floor of the courthouse, where the case had been heard.
The five-week trial in the Manhattan Criminal Court heard how the backdrop to the crime was a scandal in the Trump campaign a month before the 2016 election.
A video tape from the TV show Access Hollywood was made public, in which Trump was caught on a microphone talking in lewd terms about groping women ("When you’re a star they let you do it, grab them by the p***y. You can do anything.")
The trial heard how it was viewed as a "crisis" within Team Trump and that the campaign was soon facing another.
Ms Daniels, an adult film actor, claimed she had a sexual encounter with Trump in Lake Tahoe, Nevada, in 2006.
Fast-forward 10 years and, as he ran for office, she was hawking her story.
The details, as heard in this trial, were that she had met Trump at a golf tournament, and he had invited her to dinner.
She arrived at his hotel suite to find him dressed in satin pyjamas, until she asked him to change.
At one point, he produced a magazine, and she told the court she spanked him "right on the butt".
Later, she emerged from the bathroom to find him lying on the bed in a T-shirt and boxer shorts, and they ended up having sex.
Trump denies the liaison took place.
’Catch and kill’
Her plan to sell her story was communicated to Trump by David Pecker, former publisher of the National Enquirer magazine.
He was a friend of Trump and operated a "catch and kill" scheme on his behalf, to catch negative stories and kill them before they could be published.
He had already paid $150,000 (£117,000) to silence Karen McDougal, a Playboy model with a story of a 10-month affair with Trump.
Trump also denies the affair ever took place.
Mr Pecker told the court he had attended a meeting at Trump Tower, New York, in August 2015 with Trump and Michael Cohen, Trump’s lawyer and fixer.
At the meeting, Mr Pecker told Trump he would be his "eyes and ears".
Michael Cohen testified that, upon learning that Ms Daniels planned to sell her story, Trump told him: "This is a disaster, a total disaster. Women are going to hate me.
"This is really a disaster. Women will hate me. Guys, they think it’s cool. But this is going to be a disaster for the campaign."
Subsequently, Cohen paid Ms Daniels $130,000 (£102,000) to buy and bury the story.
Critically, he testified that he did so at Trump’s direction, placing the former president at the heart of the conspiracy.
Paying hush money is not illegal - the crime was the way in which Trump reimbursed his ’Mr Fix-It’ and the reason the money was paid.
After Trump was elected president, he repaid Cohen $420,000 (£329,000) which accounted for the $130,000 (£102,000) and other payments and bonuses, "grossed up" to account for tax liability.
The repayment was made in a series of cheques, which were recorded as legal expenses.
That was the crime - the falsification of business records, aggravated by the reason for it - the effort to conceal from voters a negative story that could have harmed Trump’s election chances.
In the words of the prosecution, it was "a planned, coordinated, long-running conspiracy to influence the 2016 election".