It's said that when Banksy first appeared on the Bristol art scene, he kept his identity secret because graffiti was illegal. However, with his global fame, popularity, and reputation as an artist now preceding him, it's hard to see how that could still be the case.
Another theory behind his anonymity is that keeping his identity a secret means he can share political messages with his followers without judgement. Over the years, various people have attempted to "out" him. In 2003, a Guardian reporter interviewed him and described him as "a 28-year-old white male with a silver tooth and a silver earring." But even that didn't really narrow things down.
One popular theory is that Banksy's real name is Robin Gunningham. Geographic profiling has revealed that the locations of some of Banksy's most famous art appears to tally up with where Gunningham was known to be at the time it appeared.
Drum 'n' bass DJ Goldie referred to the artist as "Rob" in a 2020 interview, which adds weight to the idea. However, Massive Attack co-founder Robert Del Naja has also long been rumoured to be the elusive artist, so the mystery continues.