Johanna is a fictional character appearing in the story of Sweeney Todd. In the original version of the tale, the penny dreadful The String of Pearls (1846–7), her name is Johanna Oakley and she is no relation of Todd. In the popular musical adaptation by Stephen Sondheim, inspired by Christopher Bond's play Sweeney Todd, the Demon Barber of Fleet Street (1973), she is the daughter of Benjamin Barker and his wife, Lucy. In this version she is the ward of Judge Turpin, the man who falsely convicted her father and raped her mother.

Sweeney Todd is a fictional character who first appeared as the villain of the penny dreadful serial The String of Pearls (1846–1847). The original tale became a feature of 19th-century melodrama and London legend. A barber from Fleet Street, Todd murders his customers with a straight razor and gives their corpses to Mrs. Lovett, his partner in crime, who bakes their flesh into meat pies. The tale has been retold many times since in various media.