She added: "Whatever is ahead of me is far more important than the past".
Obama also noted that, unlike Edward Snowden, Manning had faced trial and expressed contrition for what she had done. "I am looking forward to so much!" said a statement released by Manning through her legal team, the Los Angeles Times reports.
Taxpayers have paid for her transgender hormone treatments while she's been locked up.
Manning tweeted a photo, writing, "first steps of freedom".
In 2013, Manning was sentenced to 35 years in military prison, and was discharged from the USA army for her role in exposing the actions of the military. The decision angered national security experts who say Manning put USA lives at risk, but it won praise from transgender advocates who have embraced her transition to a female gender identity.
She served seven years of a 35-year sentence for leaking hundreds of thousands of diplomatic cables and military files to Wikileaks. Manning was released "in accordance to President Obama's order", the U.S. Army said in a statement, adding that no further information would be released "to ensure the privacy and security of Inmate Manning".
The AP said the leaks laid bare sensitive secrets and endangered information sources. In January, former President Barack Obama, in one of his last acts as president, commuted all but four months of her sentence.
On social media Wednesday, people either hailed her as a courageous hero or denounced her as a traitor. I pleaded guilty without the protection of a plea agreement because I believed the military justice system would understand my motivation for the disclosure and sentence me fairly. Chelsea stated before her release, she hopes to use her experience to help others.
Speaking to the BBC, Manning's friend, the journalist Glenn Greenwald - who was involved in the publication of leaks from Edward Snowden - said she faced a hard life outside prison. "Freedom used to be something that I dreamed of but never allowed myself to fully imagine". The day after she was sentenced, Manning revealed that she was a trans woman and changed her name from Bradley to Chelsea. It was not immediately clear how that would be affected by the Defense Department and Army restrictions.
The Army said on Tuesday that Manning would remainon active duty in a special, unpaid status that will legally entitle her to military medical care, along with commissary privileges.
"I think he or she should not have been released as soon", said Marian Onamer.
"Because of the nature of her circumstances and the experience of confinement, she is very committed to living her life as free from the government as possible and taking care of her own health benefits and financial needs, separate and apart from the continued benefits available to her", the lawyer said.
Tigers homer twice off Bundy, edge Orioles 6-5
Martinez now has five home runs in six games since returning from a almost eight-week stint on the disabled list on May 12. It wasn't a runaway game, but it was still a much-needed win in a season where the Tigers need all the Ws they can get.
'Big Bang Theory' Prequel 'Young Sheldon': See the First Look
The show will air on September 25 for a special launch and then move to Thursdays , airing directly after The Big Bang Theory . In the just-ended season cliffhanger, Sheldon is seen proposing to longtime girlfriend Amy, played by Mayim Bialik.
Georges St-Pierre Not Interested In Fight With Anderson Silva
And that does seem a hell of a lot more logical to everyone with regards to contenders deserving of a title shot at middleweight. They need good title fights on their pay-per-views and waiting until November is a significant delay so I understand that.