Bradley Manning says he plans to live as a woman and begin hormone therapy, a day after the soldier was sentenced to 35 years in prison for sending classified information to WikiLeaks.
He plans to live as a woman named Chelsea, he said in a written statement provided to NBC's Today show.
A military judge announced the sentence in Manning's court-martial.
Manning's struggle with gender identity disorder - his sense that he was a man trapped in a woman's body - was a key part of his defence.
Lawyers had presented evidence of Manning's struggle with gender identity, including a photo of the soldier in a blond wig and lipstick that he sent to a therapist.
Manning had faced up to 90 years in prison. Prosecutors had wanted at least a 60-year sentence, saying it would dissuade other soldiers from following in his footsteps. The defence suggested no more than 25 years so that Manning could rebuild his life.
With good behaviour and credit for the more than three years he has been held, Manning could be out in about six-and-a-half years, according to his defence lawyer David Coombs. Manning's rank was reduced, he was dishonourably discharged and he forfeited his pay.