Joe Biden has become the 46th President of the United States, while Kamala Harris is the first female to be sworn in as vice president. Here is the latest from Washington.
The newly-inaugurated President Biden and Vice President Harris have left the west side of US Capitol with their official parties.
They will see off outgoing vice president Mike Pence from the east side of the Capitol.
The symbolic gesture would usually see them say a farewell to the outgoing president, however, former president Donald Trump has opted not to attend the inauguration in a departure from tradition.
The official inauguration ceremony of the 46th President of the United States has concluded as the national colours are withdrawn.
A masked former president Barack Obama has embraced the masked President Biden and Vice President Harris.
Reverend Dr Silvester Beaman is delivering the benediction following President Biden and Vice President Harris' inauguration.
The Delaware pastor is a friend of Mr Biden.
Country singer Gareth Brooks has sung a rendition of Amazing Grace.
Amanda Gorman has become the youngest known inaugural poet at age 22, as she delivers her original composition The Hill We Climb.
"There is always light, if only we're brave enough to see it... if only we're brave enough to be it," her address concluded.
Issuing a message to those outside of the United States, President Biden says America has been tested.
"We will repair our alliances," he said.
Continuing his inauguration speech, President Biden says disagreement must not lead to disunion.
"I pledge this to you — I will be a president for all Americans," he said.
"I promise I will fight as hard for those who did not support me as for those who did."
The Taoiseach Micheál Martin has congratulated President Joe Biden and Vice President Kamala Harris on their inauguration.
“The inauguration of a new US President is a moment of hope and renewal in US political life," he said in a statement.
Mr Martin said Mr Biden was "part of our global family" with his Irish ancestors who left Mayo and Louth during the famine.
“I look forward to welcoming President Biden back to this island and deepening cooperation on global peace, climate change, economic partnership and stability," Mr Martin said.
“I also wish to pay tribute to Vice President Kamala Harris, who has created history today, and who will help form a diverse and formidable administration."
Joe Biden says "deep" forces divide the American nation.
"Racism, nativism, fear, demonisation have long torn us apart," he said.
The President said the United States faces a "perennial" battle where "victory is never assured".
"Our better angels have always prevailed. In each of these moments, enough of us have come together to carry all of us forward, and we can do that now," he said.
Joe Biden is delivering his inauguration address as President of the United States.
"This is America's day. This is democracy's day. A day of history and hope," he said.
"Today we celebrate the triumph not of a candidate, but of a cause. The cause of democracy."
Mr Biden said the peaceful transfer of power had taken place where "violence sought to shake the Capitol's very foundation" some days earlier.
Joe Biden is President of the United States.
Chief Justice of the US Supreme Court, John Roberts, administered the presidential oath to Mr Biden.
With his hand placed on a bible held by his wife, Mr Biden swore the oath of office at the US Capitol in Washington.
Singer and actress Jennifer Lopez has sung This Land is Your Land by Woody Guthrie.
Kamala Harris has been sworn in as Vice President of the United States.
Ms Harris is the first female vice president, the first of African-American and the first of South-Asian heritage.
Ms Harris was sworn in by the first Latina to serve on the US Supreme Court, Sonia Sotomayor.
Pop star Lady Gaga has sung the United State's national anthem, The Star-Spangled Banner, to begin the inauguration ceremony in Washington.
The ceremony to inaugurate Joe Biden as 46th president of the United States has begun — watch it live here:
Joe Biden and Kamala Harris have arrived at the US Capitol in Washington.
Joe Biden and his wife Jill, as well as vice president-elect Kamala Harris and her husband Doug Emhoff, attended Mass at the Cathedral of St Matthew the Apostle as part of the Inauguration Day ceremonies in Washington.
Donald Trump did follow at least one presidential tradition, with the White House saying the Republican president left behind a note for his successor, Democrat Joe Biden.
Deputy press secretary Judd Deere declined to reveal what Mr Trump wrote to Mr Biden or to characterise the sentiment in the note, citing privacy for communication between presidents.
In a departure from tradition, Donald Trump departed Washington ahead of Joe Biden’s inauguration rather than accompany his successor to the US Capitol.
The Republican president departed the White House with his wife, Melania, saying it had been a great honour to serve and vowing to return "in some form" in his final remarks.