This race to the White House has descended into one of the most vicious political contests between the two candidates.
But, their paths have crossed several times over the course of the past few decades.
Donald Trump's rhetoric went from this in 2012:
"Hillary Clinton I think is a terrific woman, I mean I'm a little biased because I've known her for years. I live in New York, she lives in New York and I've known her and her husband for years and I really like them both a lot. I think she really works hard and I think she does a good job."
To this in 2015:
"She has a lot to hide. She was the worst secretary of state in the history of the United States. She will be a terrible president."
The race for the White House will end on November 8 when Americans head to the voting booths to elect their president.
But, the story of how the two candidates got to this stage is just as gripping.
Donald John Trump was born in 1946 in Queens in New York City, the fourth of five children.
His father Fred Trump was a builder who went on to become one of New York's biggest real estate developers.
Hillary Rodham Clinton was the eldest of three born in Chicago, her parents part of the politically conservative middle class.
Clinton was an honour student in high school, while Trump was enrolled in the New York Military Academy.
In college, Clinton was president of the Young Republicans, but later became disillusioned with the party.
Meanwhile, Trump worked in his father's real estate company while studying economics at university.
In 1971, Trump took over the family business and Clinton met a guy named Bill at Yale Law School.
In the mid-70s, Trump received a one million dollar loan from his father as he made his mark on Manhattan, then going on to forge his worldwide 'Trump' brand, before filing the first of his four bankruptcies involving his hotel and casino businesses.
Bill and Hillary, meanwhile, began making their mark on the political and legal scene, with Bill as Governor of Arkansas and Hillary balancing her legal career with being a public figure.
In 1993, Hillary Clinton became the first First Lady to have her own office in the West Wing of the White House when her husband became the 42nd president of the United States.
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Then, that very famous affair in the White House with intern Monica Lewinsky occurred, which threatened to bring down the Clinton presidency.
Despite the setbacks, Hillary's rise in politics continued.
She became the Democratic senator for New York in 2000 - Trump's home turf - as her political career on the national stage took off.
This happened as Trump became the face of his hit reality TV series, 'The Apprentice', in which contestants compete for a job as an apprentice in his company, with his now famous catch phrase “you’re fired".
Eight years later, Clinton ran for the Democratic nomination for president, but lost to Barack Obama in an election that galvanised young voters.
In 2008, Trump praised Clinton following her defeat.
"I thought that they roughed her up pretty good” he said.
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“I think she's a wonderful woman. I think that she's a little bit misunderstood. Hillary's a very smart woman, very tough woman, that's fine, she's also a very nice person. And I know Hillary and I know her husband very well and they're fine people."
As Clinton went on to become secretary of state under the Obama administration, Trump was donating to her political campaigns as well as to the Clinton Foundation.
Trump also played golf with Bill Clinton, and during an appearance on the Late Show with Stephen Colbert last year, Mr Clinton admitted to meeting Trump just before he entered the presidential race.
When Donald Trump married his third wife, Slovenian born model, Melania, the Clintons attended.
"I said be at my wedding,” Trump said, “and she came to my wedding".
“I didn't know him that well,” Hillary Clinton later said.
“I mean I knew him, I knew him and happened to be in Florida and I thought it'd be fun to go to his wedding because it's always entertaining. Now that he's running for president, it's a little more troubling."
Having eliminated their opponents, they've become the fiercest of adversaries, and three presidential debates later, their relationship has turned increasingly acrimonious.
Donald Trump took aim at his opponent in May, saying: "We cannot take Hillary Clinton any more, we've had enough of Clinton", while Hillary fired her own shots, saying, "we can’t have a loose cannon in the Oval Office".
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