The following is a look at the key moments of the debate - the substance, the zingers and the insults:
Political observers expected the Republican incumbent to come out swinging, but it was the 77-year-old former vice president who ended up landing some of the toughest insults of the night, calling Trump a “clown” and a “liar.”
“Everything he’s saying so far is simply a lie. I’m not here to call out his lies,” Biden roared at one point.
At another moment, amid constant interruptions by the president, which angered even moderator Chris Wallace, Biden retorted: “It’s hard to get any word in with this clown. Excuse me, this person.”
And he said “Will you shut up, man?” - which immediately was marketed by the Biden campaign on tee-shirts.
The Democratic White House hopeful said Trump was “the worst president that America has ever had.”
But the 74-year-old real estate mogul-turned-president launched a few zingers of his own, berating Biden for criticizing his coronavirus response and saying Trump needed to get “a lot smarter” to avert more deaths.
“You graduated either the lowest or almost the lowest in your class. Don’t ever use the word smart with me. Don’t ever use that word with me. There’s nothing smart about you, Joe,” Trump fired back.
What about those taxes?
After a bombshell report from The New York Times indicating that Trump paid almost no federal income tax in both 2016 and 2017, the issue was bound to come up.
When Wallace asked Trump to directly say whether he had paid more than US$750 (B23,753) in income tax in those years, not in any other taxes, he at first deflected and when pressed, said he had paid “millions of dollars.”
“Show us your tax returns,” said Biden, who released his own 2019 return before the debate in Cleveland, showing he and his wife had paid nearly $300,000.
“You’ll get to see it,” Trump replied, without saying when.
Dragging the kids into it
Much has been said and written about Biden’s son Hunter’s business dealings in Ukraine and China. Trump has repeatedly tried to frame the issue as one showing wrongdoing by the former vice president.
“China ate your lunch, Joe. And no wonder, your son goes in, and he takes out billions of dollars,” Trump said.
Biden turned the tables, suggesting he could “talk all night” about Trump’s family and “ethics.” Trump’s daughter Ivanka works as a senior advisor to her father, and her husband Jared Kushner is a high-profile White House aide.
“My family lost a fortune coming down and helping with government,” Trump said.
Later in the debate, Trump again talked about Hunter Biden, alleging he had been “dishonorably discharged” from the military for drug use.
Biden exploded, saying: “My son, like a lot of people you know at home, had a drug problem. He’s overtaken it. He’s fixed it.”
And he mentioned his son Beau, who died of brain cancer in 2015, as a way into an attack on Trump’s reported comments about the military as “losers” and “suckers.”
“He was not a loser. He was a patriot,” said Biden.
Wallace asked both candidates to comment on the race tensions that have convulsed America in recent months, following a series of deaths of African Americans at the hands of police.
When the moderator asked Trump if he would condemn “white supremacists” and ask them to stand down, Trump said he was “willing to do that.”
But he added: “Proud Boys, stand back and stand by. But I’ll tell you what, I’ll tell you what, somebody’s got to do something about Antifa,” referring to the far-left movement.
The Proud Boys, a far-right extremist group, then appeared to adopt the phrase, with one known social media account posting a logo that read “Stand Back, Stand By.”
Accepting the election result
As the raucous debate wound to a close, Wallace asked both men if they would pledge to honor the election results. Trump has recently failed to explicitly guarantee a peaceful transfer of power, should he lose on November 3.
“We might not know for months,” Trump said, adding later: “This is not going to end well.”
“I’m urging my supporters to go into the polls and watch very carefully,” he said.
Biden pledged to respect the results “after all the ballots are counted.”
“That will be the end of it. And if it’s me, fine. If it’s not me, I will support the outcome,” he said.