President Barack Obama has commuted the 35-year prison sentence of Chelsea Manning, the soldier who leaked thousands of secret documents to Wikileaks in 2010, setting her on track for release in May.
Manning is the most high-profile of those granted clemency or presidential pardons before Mr Obama leaves office.
The White House had signalled that she was being considered for clemency, contrasting her case with that of Edward Snowden, who also leaked sensitive documents to Wikileaks before fleeing to Russia.
"Chelsea Manning is somebody who went through the military criminal justice process, was exposed to due process, was found guilty, was sentenced for her crimes, and she acknowledged wrongdoing," Josh Earnest, Mr Obama's spokesman said last week.
"Mr Snowden fled into the arms of an adversary and sought refuge in a country, that most recently made a concerted effort to undermine confidence in our democracy."
Manning attempted suicide twice last year, saying she had faced harsh treatment from officials at Fort Leavenworth military prison in Kansas and been denied sex reassignment surgery and other treatments.
Manning came out as transgender after being sentenced in 2013, changing her name from Bradley to Chelsea.
Among the materials leaked by Manning, who served as an army intelligence analyst and was deployed to Iraq, were diplomatic cables and video of an American helicopter attack that resulted in the deaths of civilians and two reporters.
Wikileaks said last week that Julian Assange, the site's publisher, would agree to extradition to the US if Manning was set free. He is currently living in the Ecuadorian embassy in London.
Chase Strangio, an American Civil Liberties Union attorney representing Manning, said the president's action will "quite literally save Chelsea's life".
"We are all better off knowing that Chelsea Manning will walk out of prison a free woman, dedicated to making the world a better place and fighting for justice for so many," Mr Strangio said in a statement.
The Welsh-Irish family of imprisoned whistleblower Chelsea Manning said they are "over-joyed" that Chelsea will soon be free.
"We are all overjoyed that Chelsea will soon be free," the family said in a statement.
"Chelsea exposed wrongdoing and was punished for being a whistleblower.
"We regret that it has taken so long for President Obama to commute the sentence and are outraged that Chelsea has been forced to endure such abusive treatment in prison.
"We agree with the UN Special Rapporteur Juan Mendez that some of this abuse amounted to torture.
"We sincerely hope that Chelsea will now be able to get on with the rest of her life and that she finds happiness and fulfilment in whatever she chooses to do.
"There will always be a welcome for her here in Wales.
"We will not be giving any interviews to the media and ask to be left in peace and for our privacy to be respected."
Mr Obama also pardoned James Cartwright, a retired Marine general, who pleaded guilty last year to making false statements to investigators. Mr Cartwright had denied leaking classified information, despite having done so.