He - or she - is perhaps the best-known artist in the world, except that few people know who they really are.
Banksy's artwork has appeared everywhere from their native UK to San Francisco, Jerusalem, Timbuktu, Melbourne and the West Bank in Palestine. But the man - or woman - themself has remained in the shadows.
There have been several guesses in the past as to Banksy's identity. Here are the frontrunners.
Robert Del Jana
Publicly Robert Del Naja is best-known as 3D, founding member and vocalist for Bristol trip-hop collective Massive Attack.
Before he found fame with the 'Unfinished Sympathy' and 'Teardop' legends, Del Naja was a graffiti artist in Bristol - the English city Banksy also calls home.
In 2010, rumours began swirling when Banksy artworks kept popping up in cities across North America where Massive Attack had shows scheduled. Music writer Craig Williams looked at other gigs the band had played, and found they often coincided with Banksy appearances, dating back to the mid-1990s.
The final piece of the puzzle is Goldie, who like Del Naja was a graffiti artist who found fame in music in the mid-1990s. Last year Goldie was being interviewed on a podcast when he let slip Banksy's first name is Robert.
"Give me a bubble letter and put it on a T-shirt and write 'Banksy' on it and we're sorted. We can sell it now. No disrespect to Robert, I think he is a brilliant artist. I think he has flipped the world of art over."
He quickly changed the subject to jazz music.
Del Naja has dismissed the rumours, saying he's friends with Banksy - but it's not him.
Robin Gunningham
What if Goldie, famous for his gold teeth jewellery, got tongue-tied and meant to say Robin?
In 2008, The Daily Mail claimed that after speaking to dozens of the artist's friends and family, it could reveal a Bristol artist by the name of Robin Gunningham was the real Banksy.
That claim was bolstered in 2016 when scientists used 'geographic profiling' on locations Banksy works had appeared in London and Bristol, and found they matched locations Gunningham was known to live and frequent, including a pub and addresses in the two cities.
"I'd be surprised if it's not [Gunningham]," Steve Le Comber, one of the scientists, told the BBC.
"What I thought I would do is pull out the 10 most likely suspects, evaluate all of them and not name any. But it rapidly became apparent that there is only one serious suspect, and everyone knows who it is."
And in July, a pre-fame artwork by Robin Gunningham emerged, and it bears a striking resemblance to the anonymous artist's famous style.
The art is a cover and inlay for a 1993 cassette album by a Bristol ska band called Mother Samosa, signed Robin Gunningham. It's believed to be the only certified piece of work signed by Gunningham, and not Banksy.
A suspected self-portrait that appeared on an east London office block bears a striking resemblance to the man outed by The Daily Mail.
And then there's video shot at the now-infamous shredding of a print of 'Girl With Balloon'. One of the cameras pans around the room, catching a man - who looks suspiciously like the man named as Robin Gunningham by the Daily Mail - taking a photo. The position the man is standing in the room matches that of a photo uploaded to the official Banksy Instagram account.
Thierry Guetta
It's been suggested the subject of Banksy's 2010 documentary Exit Through the Gift Shop, Thierry Guetta, is the artist himself. The film's producers have denied this.
"For a while we all thought that was quite funny, but it went on for so long," they said in 2010. "It was a bit disappointing when it became basically accepted as fact, that it was all just a silly hoax."
Banksy isn't a person, he's a team - or a woman
There have been rumours 'Banksy' began life as a marketing street team for Massive Attack, or is perhaps actually a woman who leads a seven-strong collective.
Woman and girls feature heavily in Banksy works, "something that isn't true of 99 percent of street art" one conspiracy theorist wrote. But several reported sightings of the alleged artist at work have, without exception, been of a man.
There have also been suggestions some of the artist's works are too complex and appear too quickly - often overnight - to be the work of a single person.
If Banksy is actually a team of people, he wouldn't be the first. Andy Warhol infamously got others to make many of his 'pop art' pieces.
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