After making the case for Joe Biden to be elected, she was joined by her husband who lauded her qualities as a potential first lady.
"For all of you out there across the country, just think of your favourite educator who gave you the confidence to believe in yourself. That's the kind of first lady... Jill Biden will be," he said.
But what do we know about the woman who could soon be joining her husband in the White House?
Personal life
Jill Jacobs was born in June 1951 in the US state of New Jersey. The oldest of five sisters, she grew up in the Philadelphia suburb of Willow Grove.
Prior to marrying Joe, she was married to former college football player Bill Stevenson.
Joe Biden lost his first wife and his one-year-old daughter in a car accident in 1972. His sons Beau and Hunter both survived the accident.
Jill says she was introduced to Joe through his brother in 1975. At that time, he was a senator, while she was still in college.
"I was a senior, and I had been dating guys in jeans and clogs and T-shirts, he came to the door and he had a sport coat and loafers, and I thought: 'God, this is never going to work, not in a million years.' He was nine years older than I am!
"But we went out to see A Man and a Woman at the movie theatre in Philadelphia, and we really hit it off," she told Vogue of the couple's first date.
She said Joe proposed to her five times before she accepted.
"I couldn't have them [Joe's children] lose another mother. So I had to be 100% sure," she explained.
The couple married in New York City in 1977. Their daughter, Ashley, was born in 1981.
Beau Biden died of brain cancer in May 2015, at the age of 46.
Mrs Biden talked about her family and the struggles they have faced as she endorsed her husband for president on Tuesday.
"I know that if we entrust this nation to Joe, he will do for your family what he did for ours - bring us together and make us whole, carry us forward in our time of need, keep the promise of America for all of us," she said.
Teaching career
Mrs Biden, 69, has spent decades working as a teacher.
She has a bachelor's degree and two master's degrees, and earned a doctorate of education from the University of Delaware in 2007.
Prior to moving to Washington, DC, she taught at a community college in the US state of Delaware, at a public high school and at a psychiatric hospital for adolescents.
She gave her address on Tuesday at her old classroom at Delaware's Brandywine High School, where she taught English from 1991 to 1993.
Mrs Biden was professor of English at Northern Virginia Community College while her husband served as vice-president.
"Teaching is not what I do. It's who I am," she tweeted ahead of Tuesday's address.
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