Noting that he was being inaugurated on the Capitol steps just two weeks after it was stormed by a "riotous mob," Mr. Biden said the country has been reminded that "democracy is precious, democracy is fragile, and at this hour, my friends, democracy has prevailed."
Read the full text of Biden's inaugural address
Chief Justice John Roberts administered the oath of office shortly before noon, when Mr. Biden officially became president. Mr. Biden addressed the nation minutes after Vice President Kamala Harris was first sworn in, making history as the first woman and person of color to become second in line to the presidency.
Mr. Biden takes over at a time of tremendous upheaval and division, fueled both by his predecessor and the coronavirus pandemic that has claimed the lives of more than 400,000 Americans.
The inauguration ceremony was unlike any the country has ever seen, with a new president addressing an empty National Mall while thousands of National Guard troops stood watch over downtown Washington. The Mall was filled with thousands of small flags representing Americans who might otherwise have been in attendance, were it not for the pandemic.
Members of Congress, Supreme Court justices and outgoing Vice President Mike Pence were on hand to witness Mr. Biden's swearing-in, with seats spaced apart to prevent the spread of the virus. Three former presidents — Barack Obama, George W. Bush and Bill Clinton — were also among those in attendance.
Former President Donald Trump, however, was not there, having left Washington earlier Wednesday morning. Mr. Trump instead addressed supporters before boarding Air Force One for the last time as president to fly to Florida. He is the first outgoing president in more than 150 years to not attend the inauguration of his successor.