I Start Counting is a 1970 British coming-of-age drama thriller film directed by David Greene and starring Jenny Agutter and Bryan Marshall. It was written by Richard Harris. The film's plot follows a teenage girl who comes to suspect that her adult stepbrother is a serial killer. It was based on the 1966 novel of the same name by Audrey Erskine Lindop.

The film was moderately controversial because of Agutter's squeaky-clean image and youth (16, playing a 14-year-old), when coupled with the film's sexual content, including a title sequence in which the camera lingers over Agutter as she gets dressed.