Mr Biden’s victory in the battleground state of Pennsylvania put him over the threshold of 270 Electoral College votes he needed to clinch the presidency, ending four days of nail-biting suspense and sending his supporters into the streets of major cities in celebration.
"The people of this nation have spoken. They have delivered us a clear victory, a convincing victory," Mr Biden told honking and cheering supporters in a parking lot in his home town of Wilmington, Delaware.
The Democrat pledged that as president he would seek to unify the country and "marshal the forces of decency" to battle the coronavirus pandemic, rebuild economic prosperity, secure healthcare for American families and root out systemic racism.
Mr Biden addressed the 70million Americans who cast ballots in support of Donald Trump, some of whom took to the streets yesterday to demonstrate against the results.
"This is the time to heal in America."
He also thanked black voters, saying that even at his campaign’s lowest moments the African-American community had stood up for him.
"They always have my back, and I’ll have yours," he said.
Mr Biden was introduced by his running mate, US Senator Kamala Harris, who will be the first woman, the first black American and the first American of Asian descent to serve as vice-president.
Congratulations poured in from abroad, including from conservative British Prime Minister Boris Johnson, Canadian Prime Minister Justin Trudeau and German Chancellor Angela Merkel, making it hard for Mr Trump to push his repeated claims, without evidence, that the election was rigged against him.
Mr Trump, who was golfing when the major television networks projected his rival had won, immediately accused Mr Biden of "rushing to falsely pose as the winner".
"This election is far from over," he said in a statement.
Mr Trump has filed a raft of lawsuits to challenge the results, but elections officials in states across the country say there has been no evidence of significant fraud, and legal experts say Mr Trump’s efforts are unlikely to succeed.
There were no signs of the violence or turmoil many had feared, and the pro-Trump protests mostly faded as the results sank in.
Prior to the election, Mr Trump refused to commit to a peaceful transfer of power if he lost, and he falsely declared victory long before counting was complete.
Former and present political leaders also weighed in, including congratulations from former Democratic President Barack Obama and Republican US Senator Mitt Romney. Trump ally Senator Lindsey Graham called on the Justice Department to investigate claims of voting irregularities.
Biden’s win ends Trump’s chaotic four-year presidency in which he played down a deadly pandemic, imposed harsh immigration policies, launched a trade war with China, tore up international agreements and deeply divided many American families with his inflammatory rhetoric, lies and willingness to abandon democratic norms.
When Mr Biden enters the White House on January 20, the oldest person to assume the office at age 78, he likely will face a difficult task governing in a deeply polarised Washington, underscored by a record nationwide voter turnout.
Both sides characterised the 2020 election as one of the most crucial in US history, as important as votes during the 1860s Civil War and the 1930s Great Depression.
Mr Biden’s victory was driven by strong support from groups including women, African Americans, white voters with college degrees and city-dwellers. He beat Trump by more than four million votes in the nationwide popular vote count.
Mr Biden, who has spent half a century in public life as a US senator and then vice-president under Trump’s predecessor Barack Obama, will inherit a nation in turmoil over the coronavirus pandemic and the related economic slowdown, as well as protests against racism and police brutality.
Mr Biden has said his first priority will be developing a plan to contain and recover from the pandemic, promising to improve access to testing and, unlike Mr Trump, to heed the advice of leading public health officials and scientists.
