An emboldened Donald Trump has declared that "America's decline is over" as he reclaimed the US presidency, promising a crackdown on illegal immigration and portraying himself as a savior chosen by God to rescue a faltering nation.
"From this moment on, America's decline is over," Trump, 78, said inside the Rotunda of the US Capitol on Monday.
The inauguration completes a triumphant return for a political disruptor who was twice impeached, survived two assassination attempts, was convicted in a criminal trial and faced charges for attempting to overturn his 2020 election loss.
He is the first president in more than a century to win a second term after losing the White House and the first felon to occupy the White House.
"I was saved by God to make America great again," Trump said, referring to a gunman's bullet that grazed his ear in July.
Trump outlined a series of sweeping executive orders, the first steps in enacting a far-reaching agenda to expand America's territory, curb immigration, boost fossil fuel production and roll back environmental regulations.
He faces an arduous task delivering on his stated promise of a "Golden Age of America" in the face of a closely split Congress, inevitable lawsuits and recalcitrant world leaders.
He did not take immediate action on the economy or inflation, two issues that helped him win re-election.
He said he would declare a national emergency at the southern border with Mexico, dispatch troops there and resume a policy forcing asylum-seeking migrants to wait in Mexico for their US court hearings - all a prelude to what he described as an unprecedented operation to deport millions of immigrants. Republican colleagues applauded and Democrats sat stone-faced.
Shortly after the inauguration, US border authorities said they had shut down a program that allowed hundreds of thousands of migrants to enter the US legally by scheduling an appointment on an app. Existing appointments were cancelled.
While Trump sought to portray himself as a peacemaker and unifier during his half-hour speech, his tone was often sharply partisan. He repeated false claims from his campaign that other countries were emptying their prisons into America and voiced familiar grievances over his criminal prosecutions.
With outgoing President Joe Biden seated nearby, Trump issued a stinging indictment of his predecessor's policies from immigration to foreign affairs.
"We have a government that has given unlimited funding to the defence of foreign borders, but refuses to defend American borders, or more importantly, its own people," Trump said.
Numerous tech executives who have sought to curry favour with the incoming administration - including the three richest men in the world, Tesla and SpaceX CEO Elon Musk, Amazon founder Jeff Bezos and Meta CEO Mark Zuckerberg - had prominent seats on stage, next to cabinet nominees and members of Trump's family.
Trump said he would send astronauts to Mars, prompting Musk - who has long talked about colonising the planet - to raise his fists.
Trump vowed to change the name of the Gulf of Mexico to the Gulf of America and repeated his intention to take back control of the Panama Canal, one of several foreign policy pronouncements that have caused consternation among US allies.
Following his address, Trump stopped by the Capitol's visitor centre and delivered a longer, informal speech to supporters in which he voiced suspicion about election processes, characterised those imprisoned for taking part in the January 6, 2021, attack on the Capitol as "hostages" and suggested the congressional probe into the events of that day was illegal.
Trump took the oath of office to "preserve, protect and defend" the US Constitution at midday, administered by Chief Justice John Roberts. His vice president, JD Vance, was sworn in just before him.
Outgoing Vice President Kamala Harris was seated next to Biden in a section with former Presidents Barack Obama, George W Bush and Bill Clinton. Former Secretary of State Hillary Clinton, who lost to Trump in 2016, sat with her husband Bill. Michelle Obama chose not to attend.
The ceremony was moved indoors due to the extreme cold gripping much of the country.
Biden, in one of his last official acts, pardoned several people whom Trump has threatened with retaliation, including General Mark Milley, a former chairman of the Joint Chiefs of Staff who Trump has suggested should be executed for holding back-channel talks with China. Milley's portrait was removed from the Pentagon shortly after Trump's inauguration.
He also pardoned five family members minutes, citing fears that Trump would target them.
Trump said he would issue orders to scrap federal diversity programs and require the government to recognise only genders assigned at birth.
"As of today, it will henceforth be the official policy of the United States government that there are only two genders, male and female," Trump said.
Trump will not immediately impose new tariffs on Canada, China and Mexico as he has pledged to do, an official said, an unexpected development that unleashed a broad slide in the US dollar and a rally in global stock markets on a day when US financial markets were closed.
Trump's transition team asked more than a dozen nonpartisan senior diplomats to resign as part of a broader plan to replace nonpartisan civil servants with loyalists.
Even as he prepared to retake office, Trump continued to expand his business ventures, raising billions in market value by launching a cryptocurrency token that prompted ethical and regulatory questions.
The traditional parade down Pennsylvania Avenue past the White House was moved indoors to the Capital One Arena, where Trump also held a victory rally on Sunday.
