UK Home Secretary Priti Patel approved the extradition of Wikileaks founder Julian Assange to the US where he faces effectively life imprisonment.
Assange has 14 days to appeal the decision, the Home Office said.
The courts found that extradition would not be "incompatible with his human rights" and that while in the US "he will be treated appropriately".
"The UK courts have not found that it would be oppressive, unjust or an abuse of process to extradite Mr Assange," a Home Office statement read.
"Nor have they found that extradition would be incompatible with his human rights, including his right to a fair trial and to freedom of expression, and that whilst in the US he will be treated appropriately, including in relation to his health," it added.
Assange is wanted by the American authorities over documents leaked in 2010 and 2011 that exposed US war crimes in Iraq.
He has been in prison since he was removed from the Ecuadorian embassy in London in 2019, where he was earlier granted asylum, and arrested by British police. Ecuador withdrew his asylum status.
Responding to the order, Wikileaks said it was a "dark day for press freedom and British democracy".
The decision is "not the end of the fight", Wikileaks posted on Twitter, saying it would appeal the decision.
In May 2019, while serving a jail sentence in the UK for breaching bail, the US justice department filed 17 charges against Assange for violating the Espionage Act - alleging that material obtained by Wikileaks endangered lives.
Assange's legal team claimed that classified documents published by Wikileaks, which related to the Iraq and Afghanistan wars, exposed US wrongdoing and were in the public interest.
The Supreme Court ruled in March that Assange's case raised no legal questions over assurances the US had given the UK over how he is likely to be treated.
If convicted, Assange faces up to 175 years in prison.
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