Joe Biden Elected 46th President of the United States
The BBC projects that Mr Biden has won the key battleground of Pennsylvania, propelling him over the 270 electoral college vote threshold required to clinch the White House.
The Trump campaign has indicated their candidate does not plan to concede.
Mr Biden said he was "honoured and humbled" to be elected.
"In the face of unprecedented obstacles, a record number of Americans voted. Proving once again, that democracy beats deep in the heart of America," he said.
It was now time to "put the anger and the harsh rhetoric behind us and come together as a nation", he said. "It's time for America to unite. And to heal."
The result makes Mr Trump the first one-term president since the 1990s.
The BBC's projection of Mr Biden's victory is based on the unofficial results from states that have already finished counting their votes, and the expected results from states like Wisconsin where the count is continuing.
His projected win in Pennsylvania takes him to 273 electoral college votes.
The election has seen the highest turnout since 1900. Mr Biden has won more than 74 million votes so far, the most ever for a US presidential candidate. Mr Trump has drawn more than 70 million, the second-highest tally in history.