Blek le Rat (born Xavier Prou, 1952) was one of the first graffiti artists in Paris, and has been described as the "Father of stencil graffiti".

Xavier Prou was born in Boulogne-Billancourt in the western suburbs of Paris. Prou began his artwork in 1981, painting stencils of rats on the walls of Paris streets. He described the rat as "the only free animal in the city", and one which "spreads the plague everywhere, just like street art". His name originates from the comic book Blek le Roc, using "rat" as an anagram for "art".

He has had a great influence on today's graffiti-art and "guerilla-art" movements, the main motivation of his work being social consciousness and the desire to bring art to the people. British graffiti artist Banksy has acknowledged Blek's influence stating "every time I think I've painted something slightly original, I find out that Blek Le Rat has done it as well, only twenty years earlier."