The man on the Clapham omnibus is a hypothetical ordinary and reasonable person, used by the courts in English law where it is necessary to decide whether a party has acted as a reasonable person would – for example, in a civil action for negligence. The character is a reasonably educated, intelligent but nondescript person, against whom the defendant's conduct can be measured.

Clapham is a district in south west London, England, lying mostly within the London Borough of Lambeth, but with some areas extending into the neighbouring London Borough of Wandsworth.