Americans are voting in one of the most divisive presidential polls in decades, pitting incumbent Republican Donald Trump against Democrat Joe Biden.
Polls have opened in the east of the country after a long and bitter campaign amid the coronavirus pandemic.
Nearly 100 million people have already cast their ballots in early voting, putting the country on course for its highest turnout in a century.
Both rivals spent the final hours of the race rallying in key swing states.
National polls give a firm lead to Mr Biden, but it is a closer race in the states that could decide the outcome.
In the US election, voters decide state-level contests rather than an overall, single, national one.
What are the two candidates up to on Tuesday?
Both candidates are using the day as an opportunity to drive home the messages they have been hammering to voters for the last few weeks.
Mr Trump, sounding a little hoarse, spoke to Fox News by phone, saying he felt good about his chances of victory and predicting he would win “big” in key states such as Florida and Arizona.
“I think we have a really solid chance of winning,” he said. Asked when he would declare victory, he added: “When there’s victory. If there’s victory… there’s no reason to play games.”
Joe Biden visited his hometown of Scranton in Pennsylvania – a key swing state – and addressed a crowd there, saying: “It’s good to be home.”
“We’ve got to restore the backbone to this country,” he said. “The middle class built this country – Wall Street didn’t.”