Joe Biden has been sworn in as the 46th President of the United States of America at an inauguration ceremony in Washington.
With this Biden, 78, has become the oldest US president in history.
Besides, Vice President-elect Kamala Harris has also been sworn in to make another history as the first female, first Black and first South Asian vice president.
Chief Justice of US Roberts became first person to congratulate Biden.
Democrat Joe Biden assumed the helm of a country beset by deep political divides and battered by a raging coronavirus pandemic. Some 25,000 troops are guarding the inauguration ceremony after a deadly riot at the Capitol earlier this month. Meanwhile, Donald Trump did not attend his successor's inauguration - only the fourth president not to do so.
Top Republicans, including Vice President Mike Pence and the party's congressional leaders, attended Biden's inauguration, along with former US Presidents Barack Obama, George W. Bush and Bill Clinton.
Biden takes office at a time of deep national unease, with the country facing what his advisers have described as four compounding crises: the pandemic, the economic downtown, climate change and racial inequality. He has promised immediate action, including a raft of executive orders on his first day in office.
Biden was sworn in using family Bible that he also used in 2009 and 2013. When Joe Biden is sworn in as the 46th president, it was expected he will have his hand where it has been every time he's taken an oath of office before – on the Biden family Bible.
The Bible is five inches thick, features a Celtic cross on the cover, and has been in the Biden family since 1893. Biden used the Bible each time he took the oath as vice president and for each of his seven Senate swearings-in, starting in 1973. The Bible was used during his swearing-in as Vice President in 2009 and 2013.
In 2009, Biden's final oath in the Senate was delayed when the Bible couldn't be located, the Wilmington News Journal reported. Beau Biden, Biden's son who died in 2015, also used the Bible when he was sworn in as attorney general of Delaware in 2007.
Earlier in the day, Trump 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. In the final hours of his presidency, Trump pardoned 73 people, including his former adviser Steve Bannon. But he did not issue pre-emptive pardons for himself or family members.