Tens of millions of Americans are preparing to cast their votes to decide whether Donald Trump or Hillary Clinton will be the next president of the United States.
The two candidates have fought one of the most contentious political races of all time, with their campaigns dogged by controversies ranging from sexual assault allegations against Mr Trump to FBI probes into Mrs Clinton's email use.
Polls suggest Democrat Mrs Clinton has a narrow lead ahead of Tuesday's vote as she aims to become the first woman to take the top job in the White House - nearly 16 years after her husband Bill left the role.
At the age of 70, Republican Mr Trump would be the oldest person to assume the presidency if he wins, with victory marking a rapid rise to political power for the billionaire tycoon and former star of The Apprentice in the US.
Since announcing his intention to run for the White House in June 2015, Mr Trump has campaigned under his promise to "Make America Great Again", but has faced widespread criticism for some of his comments and proposed policies.
He was accused of racism over his call for a temporary ban on Muslims entering America and his plan to build a wall on the US-Mexico border after branding Mexican immigrants as rapists and criminals.
The later stages of his campaign were also plunged into turmoil after a 2005 video recording emerged in which he made lewd comments about women and bragged about grabbing them "by the p***y".
It prompted senior figures from within his own party to urge him to drop out of the presidential race and a number of women have since come forward accusing Mr Trump of sexually assaulted them - allegations he has vehemently denied.
Mrs Clinton has also faced her own controversy over her use of a private email server for work correspondence while she was US secretary of state.
While an FBI investigation in July concluded that no criminal charges should be brought, the agency's director James Comey announced the case was being reopened just days before election day after new emails "pertinent" to the investigation were discovered.
Mr Trump, who has claimed Mrs Clinton should be in jail over the email scandal, has also taken aim at her treatment of women who accused her husband Bill of sexual misconduct.
He met women who accused the former US president of rape and other unwanted sexual advances and said Mrs Clinton should be "ashamed" for attacking her husband's accusers.
Mr Clinton has never faced any criminal charges in relation to the allegations and a lawsuit over an alleged rape was dismissed.
After a frantic final few days campaigning, both Mr Trump and Mrs Clinton will be in New York on election night, with the Republican billing his planned event at a Hilton hotel as a "victory party".
Security is expected to be tight as Americans go to the polls after US authorities received intelligence of a possible pre-election al Qaida attack, with New York, Virginia and Texas reportedly mentioned as targets.
In many states people have been able to vote in advance, with around a third of ballots already cast before November 8.
Barack Obama will remain in the White House until January 20 when the election winner will take the oath of office and become the 45th president of the United States.
Other candidates running for the presidency include Gary Johnson of the Libertarian Party, the Green Party's Jill Stein and conservative independent Evan McMullin.