With the White House rivals in a dead heat six weeks before election day, Clinton from the get-go painted her Republican rival as out of touch and having a tenuous relationship with the truth, willing to say "crazy things" to get elected.
"You live in your own reality" said the 68-year old Democrat, who accused Trump of launching his political career on a "racist lie" -- the birther conspiracy theory that questioned President Barack Obama's citizenship.
Trump, who faces tough questions about his suitability for the Oval Office, started out with a more restrained tone -- he even ditched his red power tie for a more statesmanlike blue.
But he quickly went on the offensive, repeatedly interrupting Clinton with verbal jabs.
The celebrity businessman branded Clinton a "typical politician. All talk, no action. Sounds good, doesn't work."
'Trumped up, trickle-down'
In feisty exchanges on the economy, Trump reprised the themes that have catalyzed his improbable campaign, blaming Clinton and the political class for losing jobs to Mexico and China through bad trade deals.
"Our country is suffering because people like secretary Clinton have made such bad decisions in terms of our jobs and in terms of what's going on," he said.
He demanded Clinton -- a former secretary of state, first lady and US senator -- account for her time in government: "You've been doing this for 30 years. Why are you just thinking about these solutions right now? For 30 years, you've been doing it."
Clinton responded by accusing Trump of having "stiffed" small businesses throughout his business career.
Demanding Trump release his taxes, in keeping with election custom, she accused him of backing an economic platform amounting to "the most extreme" package of tax cuts for the wealthy in US history.
"I call it trumped up trickle-down, because that's exactly what it would be," she quipped.
Trump said he would release his tax returns, "when she releases her 33,000 e-mails that have been deleted," alluding to the Democrat's use of a private email server as secretary of state.
Former President Bill Clinton and Chelsea Clinton, daughter of Hillary Clinton listen during the presidential debate (AAP) Source: AAP
Super Bowl of politics
This Super Bowl of politics took place at Hofstra University on Long Island, a mere 60-minute drive from Manhattan and chaired by NBC Nightly News anchor Lester Holt.
This first 2016 presidential debate could be pivotal in deciding whether Clinton will become the first woman president, or if Trump can pull off the greatest upset in US political history.
When the celebrity businessman launched his campaign in June 2015, bookmakers put his odds at 100/1 and he was roundly mocked.
But the 70-year-old weathered allegations of bigotry and sexism to triumph in a vicious Republican primary campaign.
He now has a real shot at being sworn in as the 45th president of the United States on January 20.
Six weeks out from election day the polls have tightened to a virtual dead heat.
Trump's biggest handicap may be accusations that he has a weak grasp of policy -- which he sought to counter by accusing his rival of sowing chaos in the Middle East during her tenure as secretary of state.
"It's a total mess, under your direction, to a large extent," Trump said.
But he appeared on shaky ground as he defended his refusal to reveal his plan for defeating the Islamic State group.
"You're telling the enemy everything you want to do. No wonder you've been fighting ISIS your entire adult life," he said of the group that only came to prominence in the last decade.
Clinton -- perhaps the most qualified presidential candidate since George Bush senior or Dwight Eisenhower -- has a massive organizational advantage, a bigger campaign warchest, a lead in the popular vote and is in a notably stronger position state-by-state.
But she remains deeply unpopular. In a country split 50/50 between Democrats and Republicans, only 40 percent of voters say they have a favorable view of her.
In the last two presidential elections, young, black, Hispanic and Asian-American voters turned out in record numbers for Obama.
Clinton's campaign has struggled so far to match that level of enthusiasm.
Only 47 percent of voters aged 18 to 34 say they will definitely vote this time round, that is down from 74 percent when Obama was first elected.
From left, Melania Trump, Ivanka Trump, Pence, Karen Pence, retired Gen. Michael Flynn, and former New York Mayor Rudy Giuliani at the presidential debate (AAP) Source: AAP
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