Biden, 78, will become 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 as well as security concerns following the January 6 assault on the US Capitol by Trump supporters.
Trump left the White House for the final time just after 8 a.m. (1300 GMT) by helicopter on his way to a sendoff event at Joint Air Force Base Andrews, although top Republicans, including Vice President Mike Pence, were not expected to see him off.
The president's refusal to greet his successor before attending the inauguration represents a break with more than a century and a half of political tradition, seen as a way to affirm the peaceful transfer of power.
With only a small number of attendees present, Biden will take the oath of office before US Chief Justice John Roberts just after noon (1700 GMT), placing his hand on an heirloom Bible that has been in the Biden family for more than a century.
His 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 US Supreme Court Justice Sonia Sotomayor, the court's first Latina member.
The ceremony will unfold in front of a heavily fortified US Capitol, where a mob of Trump supporters stormed the building two weeks ago, enraged by his false claims that November's election was stolen with millions of fraudulent votes.
The violence prompted the Democratic-controlled US House of Representatives to impeach Trump last week for an unprecedented second time.
Thousands of National Guard troops were called into the city after the siege, which left five people dead and briefly forced lawmakers into hiding. Instead of a throng of supporters, the National Mall will be covered by nearly 200,000 flags and 56 pillars of light meant to represent people from US states and territories.
Biden, who has vowed to "restore the soul of America," will call for American unity at a time of crisis in his inaugural address, according to advisers.
He will waste little time trying to turn the page on the Trump era, advisers said, signing a raft of 15 executive actions on his first day in office on issues ranging from the pandemic to the economy to climate change. The orders will include mandating masks on federal property, rejoining the Paris climate accord and ending Trump's travel ban on some Muslim-majority countries.
In an early sign of his plan to reach across the political aisle, Biden has invited top congressional leaders, including House Republican leader Kevin McCarthy and Senate Republican leader Mitch McConnell, to join him at church on Wednesday morning.
Pence, former US Presidents George W. Bush, Barack Obama and Bill Clinton, and both McCarthy and McConnell are all expected to attend Biden's inauguration ceremony.
Trump, who has grown increasingly isolated in the waning days of his tenure, has still not formally conceded the Nov. 3 election.
He issued more than 140 pardons and commutations in his final hours in office, including a pardon for his former political adviser, Steve Bannon, who has pleaded not guilty to charges that he swindled Trump supporters as part of an effort to raise private funds for a Mexico border wall.
But Trump did not issue preemptive pardons for himself or members of his family, after speculation that he might do so.
GRIM MILESTONES
For Biden, who long harbored presidential ambitions, the inauguration is the zenith of a five-decade career in public service that included more than three decades in the US Senate and two terms as vice president under former President Barack Obama.
But he will confront a set of overlapping crises that would challenge even someone of his political experience.
The coronavirus pandemic in the United States reached a pair of grim milestones on Trump's final full day in office on Tuesday, reaching 400,000 US deaths and 24 million infections - the highest of any country. Millions of Americans are out of work because of pandemic-related shutdowns and restrictions.
Biden has vowed to bring the full weight of the federal government to bear on the crisis, including a more robust testing and tracing program and a massive vaccination drive. His top priority is a $1.9 trillion plan that would enhance jobless benefits and provide direct cash payments to households. It will require approval from a deeply divided Congress, where Democrats will hold slim advantages in both the House and Senate.
Wednesday's executive actions, by contrast, are intended to advance Biden's priorities without the need for legislation.
The president will establish a new White House office coordinating the coronavirus response, revoke the permit granted to the contentious Keystone XL oil pipeline and end Trump's emergency declaration that helped fund a Mexico border wall, among other orders.
Jen Psaki, the incoming White House press secretary, said Biden plans additional executive orders in the coming weeks, including eliminating Trump's restrictions on transgender troops and reversing a policy blocking US funds for overseas programs linked to abortion.
Although Biden has laid out an ambitious agenda for his first 100 days, including delivering 100 million COVID-19 vaccinations, the Senate could be consumed by Trump's upcoming impeachment trial, which will move ahead even though he has left office.
The trial could serve as an early test of Biden's promise to foster a renewed sense of bipartisanship in Washington.