Earlier in the day, court documents revealed that Assange is expected to plead guilty to a US espionage charge as part of a plea deal with federal prosecutors.
"Julian Assange is free. He left Belmarsh maximum security prison on the morning of 24 June, after having spent 1901 days there. He was granted bail by the High Court in London and was released at Stansted airport during the afternoon, where he boarded a plane and departed the UK," WikiLeaks said on X.
The statement confirmed reports that Assange has a deal with the US Department of Justice, which is yet to be formally finalized.
Assange, an Australian citizen, was transferred to London's high-security Belmarsh prison in April 2019 on bail breach charges. In the US, he faced prosecution under the Espionage Act for obtaining and disclosing classified information that shed light on war crimes and human rights violations committed by US troops in Iraq and Afghanistan.