With only a small number of attendees present, Biden took the oath of office before US Chief Justice John Roberts just after noon.
Democrat Biden, 78, became the oldest US president in history at a scaled-back ceremony in Washington that has been largely stripped of its usual pomp and circumstance, due both to the coronavirus and security concerns following the January 6 assault on the US Capitol by Trump supporters. Biden was sworn in by supreme court chief justice John Roberts, and his wife, Jill Biden, held the Bible as he took the oath. The Bible has been Biden’s family since 1893 and was used during his swearing-in ceremonies as vice-president.
Joe Biden arrived at the US Capitol on Wednesday morning for his presidential inauguration, ready to take over a country battered by the coronavirus pandemic and to put an end to a tumultuous four years under President Donald Trump.
Trump, a Republican, left the White House with his wife Melania just after 8 am (1300 GMT) and went by helicopter to a sendoff event at Joint Air Force Base Andrews, where he promised supporters "we'll be back in some form" and extolled his administration's successes before flying off to Florida.
Top Republicans, including Vice President Mike Pence, were not there to see him go. Biden arrived at the Capitol just before 10:30 (1530 GMT) for his inauguration after a visit to church, where he was joined in a show of unity by the two most senior Republicans in Congress: Senator Mitch McConnell and House of Representatives Minority Leader Kevin McCarthy.
Trump flouted one last convention on his way out. His refusal to attend his successor's swearing-in breaks with more than a century and a half of political tradition, seen as a way of affirming the peaceful transfer of power.
The president did, however, leave a customary note for Biden in the Oval Office, according to a White House official, though it was not yet known what it said.
Biden's running mate, Kamala Harris, the daughter of immigrants from Jamaica and India, will become the first Black person, first woman and first Asian American to serve as vice president after she is sworn in by U.S. Supreme Court Justice Sonia Sotomayor, the court's first Latina member.
The ceremony will unfold in front of a heavily fortified U.S. Capitol, where a mob of Trump supporters stormed the building two weeks ago, fired up by his false claims that the November 3 election was stolen with millions of fraudulent votes.
The violence, which left five dead, prompted the Democratic-controlled US House to impeach Trump last week for an unprecedented second time.
Thousands of National Guard troops were stationed on Wednesday around the Capitol, where barbed wire topped high fences and both guests and members of the press passed through multiple checkpoints. Access was strictly limited and required a government-conducted COVID-19 test within 48 hours of arrival.
Former Presidents Barack Obama, George W Bush and Bill Clinton, as well as their spouses, also arrived at the Capitol. Pence and other top Republicans were on hand as well.
Instead of a throng of supporters, the National Mall was covered by nearly 200,000 flags and 56 pillars of light meant to represent people from US states and territories.
"It is grim and beautiful at the same time," US Representative Jared Huffman, a California Democrat, said of the flags filling the Mall.
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
 "Joe Biden")
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
)
){kind=small}
){kind=small}
)
)
)
)
)
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}