The brash businessman has already begun to step away from some of his rhetoric and promises he made during the presidential campaign -- ranging from how he'll treat Hillary Clinton to what he can accomplish with Congress.
Here's Donald Trump then and now.
Trump repeatedly bashed Clinton's use of a private email server during his campaign, ticking down a list of alleged misconduct and repeatedly arguing that Clinton should be behind bars as his supporters erupted in "Lock her up!" chants.
"If I win, I am going to instruct my attorney general to get a special prosecutor to look into your situation, because there has never been so many lies, so much deception. There has never been anything like it, and we're going to have a special prosecutor," he said at the second presidential debate last month
. He added that she'd be "in jail" if he were president.
"I want to move forward, I don't want to move back. And I don't want to hurt the Clintons. I really don't. She went through a lot. And suffered greatly in many different ways. And I am not looking to hurt them at all," Trump told The New York Times
on Tuesday. "It's just not something that I feel very strongly about."
On climate change
Donald Trump called climate change a "hoax" invented by the Chinese before launching his presidential campaign
In a March interview
with the Washington Post's editorial board, he said,
"I think there's a change in weather. I am not a great believer in man-made climate change. I'm not a great believer...I'm not a big believer in man-made climate change."
And in May, he said he would "cancel" the Paris climate change accord.
Trump now: "I have an open mind to it," he told the Times on the Paris deal. "We're going to look very carefully. I have a very open mind."
Asked about the scientific consensus on a connection between human activity and climate change, he added: "I think there is some connectivity. There is some, something. It depends on how much. It also depends on how much it's going to cost our companies."
One of Trump's core campaign promises was his pledge to "repeal and replace" Obamacare, which he repeatedly dubbed a "disaster" during the campaign. Now, it seems like things aren't so clear cut.
Trump then: "Real change begins with immediately repealing and replacing Obamacare," he said on the eve of the election.
"Either Obamacare will be amended, or repealed and replaced," Trump told The Wall Street Journal
, praising several provisions of the law he said he intends to keep, such as coverage for individuals with pre-existing conditions and for adults under 26 who would like to stay on their parents' health care plans.
"I like those very much," he said of those provisions.
Trump repeatedly argued the US should take a more aggressive approach to combating terrorism, including bringing back the use of the controversial torture tactic known as waterboarding.
Trump then: "I would bring back waterboarding and I'd bring back a hell of a lot worse than waterboarding," he said in a GOP debate February 6. And even in the last week of his presidential campaign, Trump bemoaned criticism of waterboarding, saying "we have to be pretty vicious."
Trump now: He now seems to be changing his mind after talking with retired Gen. James Mattis, a leading candidate to become secretary of defense.
"(Mattis) said -- I was surprised -- he said, 'I've never found it to be useful.' He said, 'I've always found, give me a pack of cigarettes and a couple of beers and I do better with that than I do with torture.' And I was very impressed by that answer," Trump told the Times.
"Look, we have people that are chopping off heads and drowning people in steel cages and we're not allowed to waterboard. But I'll tell you what, I was impressed by that answer. It certainly does not -- it's not going to make the kind of a difference that maybe a lot of people think. If it's so important to the American people, I would go for it. I would be guided by that."
On South Carolina Gov. Nikki Haley:
Trump has been meeting with a slew of his former critics as he looks to build his administration. And he's even making room for those critics in his administration.
Trump then: "The people of South Carolina are embarrassed by Nikki Haley!" he tweeted in March.
Wednesday, Trump picked her as his ambassador to the United Nations
On the New York Times
The newspaper was one of Trump's prime targets for ridicule and attack during his campaign rallies.
Trump then: "No media is more corrupt than the failing New York Times."
Trump now: "I will say, The Times is, it's a great, great American jewel. A world jewel."