Trump, 78, clinched Tuesday's election after a polarising and dizzying campaign marked by two attempts on his life and Kamala Harris' late entry into the race following President Joe Biden's surprise withdrawal.
In a concession speech at her alma mater Howard University on Wednesday, Harris sought to console the voters who had hoped she would become the first woman to win the White House.
"To everyone who is watching, do not despair," she said.
"This is not a time to throw up our hands. This is a time to roll up our sleeves."
Vice President Kamala Harris has conceded defeat in the presidential election. (AP PHOTO)
Harris said she had called Trump to congratulate him and promised to aid his transition. But she was not prepared to embrace his vision for the nation.
"While I concede this election, I do not concede the fight that fuelled this campaign," she said, as some supporters in the crowd shed tears.
"The fight for freedom, for opportunity, for fairness and the dignity of all people."
Biden planned to address the nation on Thursday.
Trump's resounding victory underscored how disenchanted Americans had become with the economy, border security and the direction of the nation and its culture.
 Voters demanded a change, even if the agent of change was a convicted felon twice impeached and no longer the Washington outsider he was in his 2016 campaign.
Trump has said he wants the authority to fire civil servants he views as disloyal and has vowed to use federal law enforcement agencies to investigate or prosecute perceived enemies, including political rivals.
Trump and his incoming vice president, US Senator JD Vance, are due to take office on Inauguration Day, January 20.
He promised roles in his administration to Tesla CEO Elon Musk, the world's richest man and a prominent Trump donor, and former presidential candidate Robert F Kennedy Jr.
The outcome defied polls that showed a razor-close race ahead of Tuesday's Election Day.
Trump prevailed in at least five of the seven battleground states to push him over the 270 Electoral College votes needed to win the presidency and was leading in the remaining two, Arizona and Nevada, where votes were still being tallied.
Donald Trump and his incoming vice president JD Vance will take office in January 2025. (AP PHOTO)
Trump was also on track to become the first Republican presidential candidate to win the popular vote since George W Bush two decades ago.
His fellow Republicans wrested control of the US Senate from Democrats and had added to their narrow majority in the US House of Representatives, though the outcome there may not be known for several days with dozens of races still uncalled.
"It was a hell of a good day," said Mitch McConnell, the longtime Senate Republican leader.
Unified Republican control on Capitol Hill would clear the way for major portions of Trump's legislative agenda, as it did in the first two years of his 2017-2021 presidency when Republicans whipped a major tax-cut bill through Congress that mainly benefited the wealthy.
"America has given us an unprecedented and powerful mandate," Trump said early on Wednesday to a roaring crowd at the Palm Beach County Convention Center in Florida.
Major stock markets around the world rallied following Trump's victory, and the dollar was set for its biggest one-day jump since 2020.
Trump was elected despite persistently low approval ratings, four criminal indictments and a civil judgment against him for sexual abuse and defamation.
In May, Trump became the first former US president to be convicted of a crime when a New York jury found him guilty on 34 felony counts of falsifying business records to cover up hush money paid to a porn star.
Trump's political career appeared over after his false claims of election fraud led a mob of supporters to storm the US Capitol on January 6, 2021, in a failed bid to overturn his 2020 defeat.
His efforts to reverse his defeat led to two separate indictments, though all the criminal cases against him are expected to end after his victory.
Trump swept away challengers inside his party and then beat Harris by capitalising on voter concerns about high prices and what Trump claimed falsely was a rise in crime due to illegal immigration.
Trump's win will have major implications for US trade and climate change policies, Americans' taxes and immigration, and US foreign policy, including in the Middle East and Ukraine.
Trump's tariff proposals could spark a fiercer trade war with China and US allies, while his pledges to reduce corporate taxes and implement a spate of new cuts could balloon US debt, economists say.
