Banksy is a famous - but anonymous - British graffiti artist. He keeps his identity a secret.
He produces pieces of work which pop up in public places, such as on the walls of buildings.
A lot of his art is done in a particular style which people can easily recognise.
He began spray-painting trains and walls in his home city of Bristol in the early 1990s. Bristol is well known for its colourful street art and graffiti.
But in the 2000s, he expanded his work beyond Bristol and was soon leaving his artistic mark all over the world.
Graffiti is one of the few tools you have if you have almost nothing.
He quickly became well known as an artist who would poke fun at big companies and send political messages through his work.
His identity is unknown, despite lots of people trying to guess who he is.
In 2008 the newspaper, The Mail on Sunday revealed who they thought he was.
In June 2017, a DJ referred to Banksy as a man called 'Rob' in an interview.
But despite rumours about who he might be, Banksy's true identity has never been revealed.
If you want to say something and have people listen, then you have to wear a mask.
Banksy was heavily influenced in his early days by a French graffiti artist called Blek le Rat. Not only did this artist inspire Banksy politically, but Banksy was also inspired by his use of stencils.
Banksy took on this visual style for himself and, to this day, uses stencils to do a lot of his work.
This allows him to create his paintings with great detail in a short amount of time - and has also helped him to remain anonymous.
His artwork can be rebellious and is known for delivering political messages.
There are lots of people who love what he does, paying many thousands of pounds for it and considering it to be incredible art.
But there are others who don't support what he does and consider it to be vandalism.
Some of his graffiti has been painted over soon after it appears.
There is a debate about why Banksy's work can be protected as 'art' when other graffiti artists are prosecuted and sometimes even put in prison for doing the same thing.
Some of his work is also controversial because of what he does with it.
At an exhibition of his work in London in 2005, he released 200 live rats in the gallery. Rats are a common theme in his work.
Banksy was enough of an artistic celebrity by the early 2000s that his work would sell for a lot of money.
In an auction in 2008, a piece of work called Keep It Spotless was sold for just over £1 million.
In the same year, a mobile home that had a piece of Banksy artwork on it was given a £500,000 price tag. This was all because of the artwork that it had on the side.
When Banksy leaves his artwork on buildings, there can sometimes be arguments about who owns the pieces and what should be done with them, as they are very valuable.
Sometimes people want to sell them to raise money for a cause, while others think the works should be left to be enjoyed by others.