The UK's highest court denied Assange's bid because the application did not raise an arguable point of law. Assange faces espionage charges relating to WikiLeaks' release of confidential US military records about the wars in Iraq and Afghanistan.
Assange could potentially face a 175-year jail sentence, though US officials said, if he's convicted, his sentence would be between four and six years.
Interior Minister Priti Patel, who comic Alexi Sayle once said was the sort of woman who would power down your life support machine to charge her iPhone, must now ratify the extradition decision.
Then Assange can then challenge via judicial review.
Assange's US-based lawyer Barry Pollack said: "Assange will continue the legal process fighting his extradition to the United States to face criminal charges for publishing truthful and newsworthy information."