Hillary Clinton says she is running for president in 2016 and wants to be the country's "champion."
The former secretary of state and past first lady made the announcement in an Internet video on April 12.
Earlier, Clinton's campaign chairman John Podesta, said in a widely reported e-mail shared on Twitter that she would run.
"It's official: Hillary's running for president," Podesta said.
Clinton lost the 2008 nomination to Barack Obama.
Clinton appears unlikely to face a formidable primary opponent, though a handful of lower-profile Democrats have said they are considering campaigns.
Should she win the nomination, Clinton would face the winner of a Republican primary field that could feature as many as two dozen candidates, including former Florida Governor Jeb Bush, the brother and son of former presidents.
Based on reporting by AP and AFP