To his supporters, the Australian is a digital rights crusader leading the battle between hi-tech activists against mighty governments.
To his supporters, the pale, lanky Australian ex-hacker in a cramped office at the embassy is a digital rights crusader leading the battle between hi-tech activists against mighty governments.
He has defied the US army and the Central Intelligence Agency with a torrent of damaging leaks that has led some officials in the United States to call for his imprisonment.
The 45-year-old and his supporters believe the long-running Swedish case was in fact a trick to have him extradited to the United States and tried for publishing government secrets.
That suspicion has appeared increasingly probable after US Attorney General Jeff Sessions in April said that Assange's arrest was a US "priority".
Assange has compared living inside the embassy -- a gardenless apartment in the plush Knightsbridge district, opposite Harrods department store -- to life on a space station.
Assange only very rarely emerges on the embassy balcony, citing concerns for his personal safety, but frequently takes part in media conferences and campaigns via video link.
His radical anti-secrecy agenda has polarised opinion between those who hail him as a hero, and critics who say WikiLeaks has put lives in danger by releasing confidential government documents.
Ironically, Assange himself is highly secretive, although it remains unclear whether this was always so.
Born on July 3, 1971 in Townsville in Queensland, Assange has described a nomadic childhood and claims he attended 37 schools.
Living in Melbourne in the 1980s and 1990s, the teenage Assange discovered a talent for computer hacking.
But he was soon charged with 30 counts of computer crime, including allegedly hacking police and US military computers.
He admitted most of the charges and walked away with a fine.
After the launch of WikiLeaks in 2006 he was constantly on the move, bouncing between cities and frequently changing his phone number.
Created by a group of like-minded activists and IT experts, WikiLeaks was built on a simple concept: through a secure online "drop box," it would let whistleblowers leak classified information without fear of exposure.
Assange made its first big headlines in April 2010 with the release of footage showing a US helicopter shooting civilians and two Reuters staff in Iraq.
And later that year, it captured the world's attention with a series of mass document "dumps."
Some 77,000 secret US files on Afghanistan went online in July, followed by 400,000 so-called "Iraq war logs" in October.
The next month, the website caused its biggest shockwaves to date by beginning to publish more than 250,000 diplomatic cables from 274 US embassies.
WikiLeaks won a huge left-of-centre following for its exposure of the secrets of the powerful -- but enraged governments, particularly the United States.
That antipathy has only deepened after WikiLeaks released a damaging trove of hacked emails from presidential candidate Hillary Clinton's campaign and the Democratic Party.
In March of this year, WikiLeaks released documents showing how the CIA exploits vulnerabilities in popular computer and networking hardware and software to gather intelligence.
The notion of being spied on by electronic appliances such as televisions made headlines around the world.
Allegations of rape and sexual assault stemming from encounters with two women in Sweden first emerged in August 2010, although the sexual assault accusations have since expired under a statute of limitations.
On Friday, Swedish prosecutors said they were also dropping the investigation against him.
Just days before WikiLeaks began publishing the diplomatic cables in November 2010, Swedish authorities issued a pan-European warrant for his arrest.
Assange was arrested one month later in London.
He has lived in the Ecuadoran embassy since June 2012 after exhausting his British legal options.
A UN panel has said that Assange had been "arbitrarily detained" and should be able to claim compensation from Britain and Sweden.
The two countries have dismissed the report.
Assange has at least two children and said that his cat at the embassy -- which he has given the Twitter account @embassycat -- was a gift from them.