Manning had been serving a 35-year sentence for sharing classified documents with Wikileaks, and was released after President Barack Obama commuted the final 28 years of that sentence in January.
Manning came out as transgender after her conviction and fought to receive hormone treatment while imprisoned.
"Okay, so here I am everyone!!" Manning wrote in the caption of her Thursday Instagram post.
"For the first time, I can see a future for myself as Chelsea," Manning wrote in a statement before her release. "I can imagine surviving and living as the person who I am and can finally be in the outside world."
Manning had been convicted in 2013 for leaking more than 700,000 U.S. government documents to WikiLeaks. She amassed a strong support base of people who advocated on her behalf during her time in prison.