The two candidates were neck and neck in the polls after a dramatic campaign that saw two assassination attempts against Donald Trump and the shock withdrawal of President Joe Biden from the race.
Donald Trump is projected to have won North Carolina, one of the key battleground states that could decide the US election.
Millions of Americans have been voting in an historic contest that could put the Republican back in the White House or make Democrat Kamala Harris the first woman to become US president.
Polls have closed in the majority of states, with early projections coming in through the night.
North Carolina, now projected to have been won by Mr Trump, is one of seven battleground states thought to be key to taking the White House.
Of the others, Mr Trump is ahead in Pennsylvania, Georgia, North Carolina, Arizona and Wisconsin, while Ms Harris leads in Michigan.
What results are in so far?
Voting is still happening in some states, while counting is now under way in a slew of states where polls have already closed.
While not all the votes have been counted, a winner can be projected in a number of states.
Ms Harris is projected to have won California, Colorado, Connecticut, Delaware, the District of Columbia, Hawaii, Illinois, Maryland, Massachusetts, New York, Oregon, Rhode Island, Vermont, Virginia and Washington. This would put her on 189 Electoral College votes.
Mr Trump is projected to have won Alabama, Arkansas, Florida, Idaho, Indiana, Iowa, Kansas, Kentucky, Louisiana, Mississippi, Missouri, Montana, Nebraska (three of five votes), North Carolina, North Dakota, Ohio, Oklahoma, South Carolina, South Dakota, Tennessee, Texas, Utah, West Virginia and Wyoming. This would put him on 230 Electoral College votes.
None of the seven battleground states have yet been projected for either candidate. NBC News says Michigan, Pennsylvania and Wisconsin are too close to call.
Voters are not just selecting a president. Control of both the House of Representatives and the Senate are also up for grabs, with all seats in the House and one-third of those in the Senate up before voters.
With most races still not yet called, NBC News has projected that Republicans have gained a Senate seat in West Virginia. It had been held by independent Senator and former Democrat, Joe Manchin.