Sweeney Todd is a character who first appeared as the protagonist and main villain of a penny dreadful serial entitled The String of Pearls (1846-1847). Claims that Sweeney Todd was a real person are strongly disputed by scholars, although there are possible legendary prototypes, arguably making the story of Sweeney Todd an example of an urban legend.

In the original version of the tale he is a barber who murders wealthy customers by pulling a lever while they are in his barber's chair which, unknown to them, is fixed to a revolving trap-door, making them fall backward into the basement, generally causing them to break their necks or skulls as they hit the ground. Just in case they are alive, he goes to the basement and "polishes them off," meaning he slits their throats with a cut-throat razor. But in many adaptations of the tale, the murdering process is reversed, meaning that he slits their throats and then pulls a lever causing them to drop into the basement. After Todd has robbed his dead victims of their goods, Mrs. Lovett, his partner in crime (in some later versions, his friend who wants to become his lover), assists him in disposing of the bodies by having their flesh baked into meat pies, and selling them to the unsuspecting customers of her pie shop. Todd's barber shop is situated at 186 Fleet Street, London, next to St. Dunstan's church, and is connected to Mrs. Lovett's pie shop in nearby Bell Yard by means of an underground passage.

The tale surrounding the character became a staple of Victorian melodrama, and later a Tony award-winning Broadway musical in 1979. Sweeney Todd has also been featured in several films, the most recent being Sweeney Todd: The Demon Barber of Fleet Street (2007), directed by Tim Burton, with Johnny Depp in the title role.