Kamala Harris’s appointment is a historic first for American women of color.
She was a formal rival to Joe Biden in the White House race.
The long-waited announcement capped months of searching for a Democratic partner to challenge President Donald Trump’s re-election in November.
In describing his running mate, the 77-year-old Democratic presidential nominee said that Kamala Harris is a "fearless fighter for the little guy, and one of the country's finest public servants”.
If Joe Biden and Kamala Harris is elected for the highest seat in US politics, she would be the first female and first black Vice-President in America.
"I'm proud now to have her as my partner in this campaign."
The decision, announced in typical 2020 style on social media, was a crucial moment for Biden as he aims to build a broad coalition of voters to oust Trump from the White House.