CBS, NBC and CNN news networks announced the result just before 11:30 am (1630 GMT) as an insurmountable lead in Pennsylvania took Biden, 77, over the top in the state-by-state count that decides the presidency.
“America, I’m honored that you have chosen me to lead our great country,” Biden said in a statement.
“The work ahead of us will be hard, but I promise you this: I will be a president for all Americans – whether you voted for me or not. I will keep the faith that you have placed in me.”
Trump quickly responded to the announcement by accusing Biden of falsely declaring himself the next president.
“We all know why Joe Biden is rushing to falsely pose as the winner, and why his media allies are trying so hard to help him: they don’t want the truth to be exposed,” Trump said in a statement.
“The simple fact is this election is far from over.”
For Biden, who got more than 74 million votes, a record, the triumph after a tense contest conducted during a global coronavirus pandemic was the crowning achievement of his half century in US politics, including eight years as deputy to the first Black US president Barack Obama.
The result condemned 74-year-old Trump — who made frantic attempts to claim fraud and stop the vote count — to becoming the first one-term president since George H. W. Bush at the start of the 1990s.
The Republican, whose marathon press conferences, tweeting and raucous campaign rallies have made him a perpetual, noisy presence at home and abroad over the last four years, had no immediate reaction.
But ever since the night after Tuesday’s election, when he prematurely claimed victory, Trump has been inhabiting a world increasingly disconnected from the reality of his approaching downfall.
Earlier Saturday, he left the White House for the first time since Election Day to play golf, tweeting: “I WON THIS ELECTION, BY A LOT!”
And in an extraordinary White House address to the nation on Thursday — with Biden’s lead in the partial results already consolidating rapidly — he claimed “they are trying to steal the election.”
Despite Trump’s protests, the returns from vote counting offices around the country kept coming all week, with no credible reports of irregularities.
And when US television networks declared that Biden had taken an insurmountable lead in Pennsylvania, that put the Democrat over the magic number of 270 electoral college votes. Trump had no way back.