Britain's highest court is the 40-year-old Australian's final avenue of appeal under UK law, having been detained in December 2010 on a European arrest warrant. He is wanted in Sweden for questioning over allegations of rape and sexual assault.
Since then he has been through round upon round of legal battles, culminating in what will be a short ruling at the Supreme Court in central London.
The judgment, expected to take around 10 minutes, will be handed down at 9:15am (1815 AEST) on Wednesday, streamed on the Sky News website and published online once delivered.
Assange will have been living under restrictions on his movement for 540 days when the verdict is handed down.
Assange's case rests on a single point -- that the Swedish prosecutor who issued a warrant for his arrest was not a valid judicial authority.
The Supreme Court president will give a summary of the point of law raised by the appeal, the court's decision, and a brief explanation of its rationale.
A lower court in Britain initially approved Assange's extradition to Sweden in February 2011. An appeal to the High Court was rejected in November, but he subsequently won permission to appeal to the Supreme Court.
If that court rejects his appeal, Assange will have exhausted all his options in Britain but he could still make a last-ditch appeal to the European Court of Human Rights in Strasbourg, France.
Assange has said he fears his extradition will eventually lead to his transfer to the United States, where US soldier Bradley Manning is facing a court-martial over accusations that he handed documents to the anti-secrecy website WikiLeaks.
The legal saga began in August 2010 when Assange was accused of raping one woman by having sex with her while she was asleep, and of sexually assaulting another woman, in Sweden.
The former computer hacker insists the sex was consensual and says the allegations are politically motivated.
Assange shot to fame earlier that same year when WikiLeaks enraged Washington by leaking thousands of secret US documents on the wars in Iraq and Afghanistan.
After he was arrested in London in December 2010 he spent more than a week in jail before being freed to live under strict bail conditions amounting to virtual house arrest.
Source: Agence France-Presse
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