Manning sent the above photo to an Army supervisor in 2010, and it was introduced into evidence at his court martial.
Bradley Manning, the US soldier who leaked secret US government documents to the Wikileaks website, has announced he wants to become a woman.
“I am Chelsea Manning,” Pte First Class Manning, 25, said in a statement to NBC’s Today programme. “I am a female.”
He said he had felt female since childhood, wanted at once to begin hormone therapy, and wished to be addressed as Chelsea.
He has been sentenced to 35 years in prison for crimes including espionage.
He could be released on parole after at least seven years in jail, his civilian lawyer David Coombs has said.
Mr Coombs has asked President Barack Obama to pardon Pte Manning, and has pledged to appeal against the verdict and sentence.
Pte Manning will serve his sentence at Fort Leavenworth, Kansas, and on Thursday, Mr Coombs indicated he was willing to take legal action to force the prison to provide hormone therapy if authorities refused.
He said Pte Manning had not indicated whether he wanted to undergo sex reassignment surgery.
“The ultimate goal is to be comfortable in her skin and to be the person that she’s never had an opportunity to be,” he said.
Asked why Pte Manning was making this announcement now, the day after his sentencing, Mr Coombs said: “Chelsea didn’t want to have this be something that overshadowed the case.”
Pte Manning’s struggles with his identity formed a key part of his defence through his weeks-long court martial.
Defence witnesses, including therapists who had treated Pte Manning, testified he had said he wanted to transition to being a woman, suggesting his problems with his gender identity affected his mental health.
US military prosecutors, meanwhile, described Pte Manning as a notoriety-seeking traitor and asked for a 60-year sentence in order to deter future intelligence leakers.
Pte Manning, who grew up in the US state of Oklahoma and in Wales, joined the Army in 2009 to help pay for university and, according to court martial defence testimony, to rid himself of his desire to become a woman. Trained as an intelligence analyst, he was deployed to Iraq in 2010.
There, he became disillusioned with the war and felt increasingly isolated from his friends and family. In May of that year, he initiated what subsequently became one of the largest leaks of classified US government documents ever – hundreds of thousands of diplomatic cables and battlefield reports from Afghanistan and Iraq.
Pte Manning has said he hoped the documents would change the world by sparking a debate about US foreign policy and the military. Since his conviction he has apologised for his actions.
At his court martial, Pte Manning’s former Army supervisor testified Pte Manning had sent him a photograph of himself wearing a blond wig and lipstick.