Biden announced his decision in a tweet on Tuesday.
“I have the great honor to announce that I’ve picked @KamalaHarris — a fearless fighter for the little guy, and one of the country’s finest public servants — as my running mate,” Biden wrote.
Biden and Harris will be confirmed during the Democratic convention which is scheduled to begin on Monday.
But who is Kamala Harris? Here’s a closer look at Biden’s running mate.
California born and raised
Harris, 55, was born in Oakland, California. She is the daughter of two immigrants.
Her mother, Shymala Gopalan-Harris — a cancer researcher — was born in India. Her father, Donald Harris, immigrated to the U.S. from Jamaica to study economics.
Harris spent most of her early life in California, but she and her younger sister Maya briefly attended high school in Canada after their mother accepted a research position at Jewish General Hospital and a teaching job at McGill University in Montreal.
After high school, Harris attended Howard University before earning her law degree at the University of California, Hastings College of the Law.
From 2003 to 2011, Harris served as the District Attorney in San Francisco.
She married lawyer Doug Emhoff in 2014 and is a stepmother to Ella and Cole Emhoff.
California Attorney General
In 2010, Harris became the first Black woman to be elected the Attorney General of California.
She was re-elected in 2014.
According to Biden, when Harris was attorney general in California, she worked closely with his late son, Beau Biden.
Beau served as the attorney general in Delaware until his death in 2015.
“I watched as they took on big banks, lifted up working people, and protected women and kids from abuse,” Biden wrote. “I was proud then, and I’m proud now to have her as my partner in this campaign.”
During her time as attorney general, Harris won a US$20 billion settlement for California homeowners against big banks that were foreclosing on homes.
However, Harris has received criticism from some in the Black community and from progressive advocates for her record as attorney general where, they say, she did not do enough to investigate police shootings and too often sided with prosecutors in wrongful conviction cases.
But her defenders say Harris has always been reform-minded and point to her record in the Senate, where she has championed a police reform bill and an anti-lynching bill, among other measures.
Harris herself has said she became a prosecutor in order to bring a more progressive approach to the office.
On to the Senate
In 2016, Harris ran for the U.S. Senate and won, becoming California’s third female senator.
She is also the second Black woman in history to be elected to the U.S. Senate.
Harris currently serves on the Senate Judiciary Committee, Homeland Security and Governmental Affairs Committee, Select Committee on Intelligence and the Committee on Budget.
She is known for her sometimes aggressive questioning style in the Senate.
In 2018, Harris made headlines for her unyielding questioning of U.S. Supreme Court Justice Brett Kavanaugh during his confirmation hearing.
Harris also briefly threw her hat into the running to become the Democratic presidential candidate.
And during several debates, Kamala set her sights on Biden, attacking the former vice-president for his record on issues of race.
However, Harris suspended her campaign in early December, citing financial troubles.
A few months later, she announced she would be endorsing Biden.
“One of the things that we need right now is we need a leader who really does care about the people and who can therefore unify the people,” Harris said in a video in March. “And I believe Joe can do that.”
Harris said Biden “has served our country with dignity and we need him now more than ever.”
“I will do everything in my power to help elect him the next President of the United States,” she said.
In a statement released shortly after Tuesday’s announcement, former U.S. President Barack Obama said Biden “nailed this decision.”
“I’ve known Senator @KamalaHarris for a long time,” he wrote. “She is more than prepared for the job. She’s spent her career defending our Constitution and fighting for folks who need a fair shake.”
“Michelle and I couldn’t be more thrilled for Kamala, Doug, Cole and Ella,” he continued. “This is a good day for our country.”
Susan Rice, who served under Obama as the White House national security advisor had also been short-listed as a potential running mate for Biden.
In a tweet after the announcement, Rice offered her “warmest congratulations” to Harris.
“Senator Harris is a tenacious and trailblazing leader who will make a great partner on the campaign trail,” she said.
“I am confident Biden-Harris will prove to be a winning ticket,” Rice continued. “I will do my utmost to help them win and govern.”
Harris is now the first Black woman to be the vice-presidential nominee for a major U.S. political party.
Speaking a press conference on Tuesday, U.S. President Donald Trump said he was “surprised” that Biden chose Harris, saying she did “very, very poorly” in the primaries.
“She’s a big tax raiser, she’s a big slasher of funds for our military and she has a lot of difficult things she’s going to have to explain,” he said.
Trump said Harris was “nasty” to Kavanaugh during his 2018 hearing.
“She was nasty to a level that was just a horrible thing, the way she was, the way she treated now Justice Kavanaugh,” he said. “And I won’t forget that soon.”
Trump continued, saying he likes Pence “much better” than Harris.
“He’s solid as a rock,” he said. “He’s been a fantastic vice president.”
Harris is scheduled to debate Pence on Oct. 7 in Salt Lake City, Utah.
— With files from Reuters and The Associated Press