WikiLeaks source Chelsea Manning released from jail
Manning "has been released from the United States Disciplinary Barracks" at Fort Leavenworth, Kansas, US army spokeswoman Cynthia Smith said in a brief statement.
In July 2010, Manning - then a male soldier known as Bradley - was arrested over the release of a huge collection of more than 700,000 classified military and diplomatic documents via WikiLeaks, one of the largest leaks of classified information in US history.
The 29-year-old spent several stints in solitary confinement while in jail, and went on hunger strike to denounce strict disciplinary measures.
Last year alone, she attempted to commit suicide twice.
In one of his final acts as president, Obama pardoned 64 people and commuted the sentences of 209 others, including Manning.
"Two more days until the freedom of civilian life," Manning tweeted Monday.
"Now hunting for private #healthcare like millions of Americans."
Manning has becoming a hugely divisive personality in the US, after she was arrested and jailed in 2010.
For some, she is a truth-seeker who sacrificed her future to expose war crimes.
But for others, her actions are seen as reckless, putting the lives of Afghans working against the Taliban at risk due to their names going public.