Donald Trump has won the US presidential election after a dominant performance that saw him flip multiple swing states and win the popular vote.

AP declared him the winner after he took the swing state of Wisconsin.

Earlier, Trump took the stage to address supporters in Florida, at about 2:30am on Wednesday, local time. At the time, the Democratic candidate Kamala Harris had no plausible path to victory, although the race was technically not over.

"This is the greatest political movement of all time," Trump told supporters at his West Palm Beach election night event.

"Now it is going to reach a new level of importance because we're going to help our country heal."

Trump becomes only the second US president to win non-consecutive terms, following in the footsteps of Democratic president Grover Cleveland, who won elections in 1884 and 1892. 

His vice-president will be JD Vance.

"America has given us an unprecedented and powerful mandate," Trump said, flanked by his family and campaign officials.

The 78-year-old, who was the target of two assassination attempts this year, said he wanted to bring Americans together.

"It's time to put the divisions of the past four years behind us," he said.

"Success will bring us together."

Harris, the current vice-president, did not make an appearance at her election-night event, at Howard University in Washington DC.

After midnight, her campaign chair Cedric Richmond briefly addressed the crowd, saying the Democratic candidate would have something to say on Wednesday, local time.

Swing states all red

Analysts predicted the election would be among the closest in US history, and while the seven swing states that had been the focus of the campaign were all tight races, the Republicans and Trump pulled ahead in all of them.

Trump performed better than polls predicted among several key sections in the electorate, including Hispanics.

The Democrats have historically enjoyed significant support from members of that community.

Once Trump's victory is confirmed, he will move back in to the White House in January — the month US presidents are inaugurated — but the good news does not stop there for Republicans, who also look likely to control both chambers of congress.

The crowd at Trump's West Palm Beach event was jubilant.

Supporters danced along to the Village People's disco classic YMCA, an anthem that has become synonymous with the Trump campaign.

What the next four years could look like 

When Trump took the stage, he reminded people of his policy agenda and paid tribute to some of his biggest backers.

Among them was RF Kennedy Jnr, who had unsuccessfully stood for the Democratic nomination, as well as run as an independent before going into Trump's tent.

It is anticipated he would have a hand in controlling US public health authorities under a Trump administration.

Trump also gave a shout out to tech billionaire Elon Musk, who is likely to have a significant role in a government run by the former president.

"He's a character. He's a special guy, he's a super genius," Trump said of Musk. 

"We have to protect our geniuses. We don't have that many of them. We have to protect our super geniuses."

Republicans have won control of the senate, retaking the chamber for the first time in four years. 

Control over the House of Representatives is still up for grabs, with over 100 races yet to be called.

Trump says he will use his likely powers to enact his legislative agenda. 

"We're going to have to seal up those borders, and we're going to have to let people come into our country," he said.

"We want people to come back in, but we have to, we have to let them come back in. But they have to come in legally."