Joe Biden is the 46th president of the United States as Donald Trump has quietly exited the White House after months of denying the election result.
Kamala Harris, meanwhile, provided a bright and history-making moment by becoming the first woman to be sworn in as vice president.
With a star-studded celebration set to continue into the night, you can follow along with all the latest updates below.
That's the end of our live rolling coverage of the Joe Biden inauguration. With the party set to go into the night, including a TV special hosted by Tom Hanks, make sure to check back at Yahoo News Australia for all the latest stories.
Biden press secretary promises to bring facts back
The incoming press secretary Jen Psaki has promised to provide a stark contrast to her many predecessors under Trump, who frequently echoed false claims by the president.
In her first remarks to the press, Psaki began by extolling the importance of transparency and trust.
"When Mr Biden asked me to take this job, we talked about the importance of bringing truth and transparency back to the briefing room.
“There will be times when we see things differently in this room. I mean, among all of us. That's okay. That's part of our democracy. And rebuilding trust with the American people will be central to our focus in the press office and in the White House every single day," she said.
Fielding her first question from the assembled media members, she was asked how she saw her role – as one to promote the interests of the president, or to “provide the unvarnished truth” to the public.
She responded by saying she understands the power of the podium she occupies "and the power of truth and the importance of setting an example of engagement and transparency".
"We have a common goal," she told the journalists."Which is sharing accurate information with the American people."
Trump was credited for ushering in the so-called 'post-truth era'. It sounds like Biden is intent on winding that back.
US rejoins global effort on climate change
As promised, Joe Biden has signed an executive order that will see the United States rejoin the Paris Climate Accord, a multilateral agreement which aims to reduce global emissions.
Early in his tenure, Donald Trump announced in June 2017 that he would be unilaterally pulling the US from the agreement.
Biden's stated plan to tackle global warming is expected to increase pressure on Prime Minister Scott Morrison and the Australian government to commit to more ambitious policies on emissions reduction.
Former vice president and leading campaigner for climate action, Al Gore, thanked the voters for making it happen.
"Thanks to American voters, we are back in the Paris Agreement," he tweeted.
"America is once again poised to lead the world on climate action, working with our allies to build a better future for us all. Time to get back to work!"
Biden wasted no time, moving with unusual haste in his first hours on the job, to sign 17 executive orders, memorandums and proclamations – of which 15 were executive orders, according to the New York Times.
Among the executive orders was a mandate for mask wearing on federal properties, ending oil and gas development at national wildlife monuments and the removal of a ban on immigration placed on some majority-Muslim countries.
Biden also ended a national emergency declaration that was the basis for diverting some federal funds to build a wall along the US-Mexico border.
Democrats control Senate for first time since 2011
Three new Democratic senators have been sworn in to office by Vice President Kamala Harris. That means their party now has control of the White House and Congress for the first time in a decade.
Raphael Warnock and Jon Ossoff both won Senate runoff elections in Georgia earlier this month, defeating Republicans Kelly Loeffler and David Perdue.
Wednesday was Harris’ first time presiding over the Senate, which the Democrats haven't controlled since January 2011.
Warnock is Georgia’s first Black senator while Ossoff is Georgia’s first Jewish senator and, at 33, the youngest sitting member.
The Senate is now divided 50-50. Democrats will be in control because the vice president casts tie-breaking votes in the chamber.
New White House takes over offical Twitter accounts
President Biden and Kamala Harris had another transfer of power today: taking control of the @POTUS and @VP Twitter handles.
The social media company that was so central to Trump's presidency has also created a brand new account for Doug Emhoff, the vice president's husband, or @SecondGentleman.
While the outgoing president was unceremoniously banned from the social media service, Biden won't have that problem, according to his staff.
Speaking to The Atlantic, a Biden transition adviser told the publication the new president would not use social media as an “abusive, psychotic mechanism to display insecurity and grievances."
Bill Clinton accused of nodding off
Biden's inaugural address has been widely praised – but not everyone was apparently enamoured with the moment.
Former Democrat president Bill Clinton was filmed appearing to momentarily fall sleep during the speech.
Clips showing the 74-year-old's eyes slowly closing were posted online after some viewers noticed the apparent moment of shut-eye.
Perhaps he was just taking it all in, but the internet was never going to let it go.
After deep clean, Biden moves into White House
After some brief quiet, and a deep clean, the so-called executive mansion began humming again with activity a few hours after Biden’s inauguration Wednesday (local time) as staff for the new president started moving into their offices, unpacking belongings and getting the badges that grant them easy access to the property, the Associated Press reported.
After three coronavirus outbreaks at the White House in recent months, an extra $US200,000 was reportedly spent to give the residence a thorough clean before the new administration arrived.
New press secretary Jen Psaki tweeted that she was “in the building and ready to get to work.” Psaki has scheduled the new administration’s first White House press briefing for later in the day.
Biden plans to sign a flurry of executive orders, some overturning actions by his predecessor, once he gets to the Oval Office in the coming hours.
According to CNN, Biden plans to sign 17 executive orders which will go some way to dismantling the legacy of Donald Trump.
Biden will halt construction of Trump's border wall, reverse his travel ban targeting Muslim countries, return the US to the Paris Climate Accord as well as the World Health Organisation and embrace progressive policies on the environment and diversity.
As Biden heads for the White House, Barack Obama tweeted words of support for his former VP, saying "it's your time".
Parade through largely empty streets dubbed 'eerie'
Before the president made tracks for his new office, the conventional inauguration parade made its way through the streets of downtown DC.
But this year, the lack of a crowd meant only journalists and a sprinkling of people were there to observe the festivities up close.
"Feels like a rehearsal," remarked Washington Post reporter Rebecca Tan.
Sanders on Trump absence: 'He's an egomaniac'
The inauguration was attended by former presidents including Barack Obama, George W Bush and Bill Clinton. And while outgoing vice president Mike Pence was there, much was made about Trump's decision to part with a long-standing tradition and boycott the event.
Senator Bernie Sanders, who at one point looked primed to clinch the Democratic nomination to challenge Trump before a surge in Biden support, derided the now former president for the move but said he appreciated the attendance of Mike Pence.
"Look, what can you say about Donald Trump? He lives in his own world, he's an egomaniac, he couldn't care less about democracy or precedent or the American people," he said on CBS after attending the inauguration.
"So of course he should do what every other president in history has done when they leave office ... to show the American people regardless of political party, we have a continuity of government ... But Donald Trump doesn't care about democracy."
Fox anchor: 'Best inaugural address I ever heard'
Veteran Fox New journalist Chris Wallace has praised Joe Biden's inaugural address as the best since John F Kennedy's famous speech in 1961.
"I have been listening to these inaugural addresses since 1961. John F. Kennedy's 'ask not'. I thought this was the best inaugural address I ever heard," he said on air.
"Obviously a lot of this event today, a lot of the president's speech was coloured by the emotion that exactly two weeks ago – 14 days ago – there was a mob of insurrectionists, of domestic terrorists on the inaugural stand."
Wallace played a notable role during the election campaign conducting a tough interview with the president and clashing with him while moderating the first presidential debate in which Wallace was criticised for not being able to rein in Trump.
In what he labelled "part sermon, part pep talk", he also praised the key tenor of Biden's address that truth matters.
"It was a call to all of us," he said, in what many online took as a slight acknowledgment of the role Fox News played in pushing the election lies of Donald Trump.
Scroll down to see highlights from Biden's address.
Military figures welcome incoming president
The official swearing-in ceremony for President Joe Biden has concluded, but more events are planned throughout the day.
Despite fears harboured by the FBI of more violent unrest, calm prevailed outside heavily fortified state capitol buildings across the US as he was sworn in.
Biden was expected to sign paperwork in the President’s Room within the US Capitol. Afterward, he reviewed troops outside the Capitol in a traditional inauguration procedure known as the Pass in Review, which is a symbolic demonstration of the military accepting the peaceful transition of power.
Biden will then travel to Arlington National Cemetery for a ceremony with former presidents in attendance, including Barack Obama and George W Bush.
Later in the day, Biden is expected to make his first official arrival at the White House as president before a virtual inaugural parade and a TV special hosted by Tom Hanks which will replace the usual inauguration ball due to Covid precautions.