The announcement was made on Friday evening, ending a long-running saga after the Australian hacker was arrested in 2019 and jailed at the maximum security prison in Belmarsh after he had been given refuge in the Ecuadorian embassy in London for seven years.
The Home Office said Assange could still appeal the decision. WikiLeaks said he would do so.
"In this case, the UK courts have not found that it would be oppressive, unjust or an abuse of process to extradite Mr Assange," the Home Office said in a statement.
Assange can appeal the extradition at London's High Court but he needs to do so in 14 days after first getting the court's approval to challenge the decision.
If that fails, he can try to approach the UK Supreme Court. In the event that an appeal is refused, he has to be extradited in 28 days.
our "allies" in the UK are willing to send julian #Assange to die in a US prison. now is when we need to make some noise, and for some @AlboMP diplomacy. tonight. end this horror: #FreeJulianAssange https://t.co/jzykokcP4O— Scott Ludlam (@Scottludlam) June 17, 2022
In a statement, WikiLeaks said: "This is a dark day for press freedom and for British democracy. Anyone who cares about freedom of expression should be deeply ashamed that the Home Secretary has approved the extradition of Julian Assange to the US, the country that has plotted his assassination."
After Australia elected a Labor government in May, there have been hopes that Prime Minister Anthony Albanese would intervene in the case and try to get Assange sent back to Australia.
Albanese hinted before the election that Assange's protracted judicial proceedings should be ended. When he was asked about it recently, he responded that diplomacy was not conducted over a megaphone.
BREAKING: Home Secretary Priti Patel approves extradition of Julian Assange to the US, a country that plotted to Assassinate him.— Double Down News (@DoubleDownNews) June 17, 2022
His crime: Journalism and exposing War Crimes to the world.
A very dark day for Press Freedom & British Democracy pic.twitter.com/4lV09I3GyE
Assange faces criminal charges in the US for publishing classified information that was leaked to WikiLeaks by an American soldier, then known as Bradley Manning, but now, after gender reassignment surgery, known as Chelsea Manning.
On 14 March, the UK Supreme Court had rejected an appeal from Assange to hear arguments against his extradition.
In January, the High Court refused a request from Assange's lawyers to appeal directly to the Supreme Court, leaving it to the higher court to decide on whether it would hear a challenge.
Home Secretary Priti Patel has approved the extradition of Julian #Assange to an American hellhole. A new appeal will now challenge the political rottenness of British 'justice'. Either we raise our voices as never before, or our silence colludes in the death of an heroic man.— John Pilger (@johnpilger) June 17, 2022
On 10 December 2021, a two-bench High Court panel reversed a 4 January lower court verdict the same year to deny the US the right to extradite Assange to try him on criminal charges in Washington.
British District Judge Vanessa Baraister had ruled in January 2021 that Assange should not be extradited, saying the risk he would commit suicide in a US jail was too high.
The decision by the UK Govt to approve extradition of Julian Assange to the US is an outrageous betrayal of rule of law, media freedom and human rights. @AlboMP must pick up the phone now and demand an end to this madness https://t.co/W0fi2lw38p. #FreeAssangeNOW #auspol #politas— Andrew Wilkie MP (@WilkieMP) June 17, 2022