The Optimists of Nine Elms, also known as The Optimists, is a 1973 British drama film starring Peter Sellers and directed by Anthony Simmons, who also wrote the 1964 novel upon which the film is based. The film is about an old street musician (played by Sellers) who strikes up a friendship with two children - Liz, played by Donna Mullane, and her younger brother Mark, played by John Chaffey. Neither of the child actors was featured in future films. A young Keith Chegwin also played a small role.

Mullane was recruited for her role by the film crew when they were scouting locations and saw her as she was walking home from school.