Sousveillance (/suːˈveɪləns/ soo-VAY-lənss) is the recording of an activity by a member of the public, rather than a person or organisation in authority, typically by way of small wearable or portable personal technologies. The term, coined by Steve Mann, stems from the contrasting French words sur, meaning "above", and sous, meaning "below", i.e. "surveillance" denotes the "eye in the sky" watching from above, whereas "sousveillance" denotes bringing the means of observation down to human level, either physically (by mounting cameras on people rather than on buildings) or hierarchically (with ordinary people observing, rather than by higher authorities or by architectural means).

Undersight (inverse oversight) is sousveillance at high-level, e.g. "citizen undersight" being reciprocal to a congressional oversight committee or the like.

Inverse surveillance is a subset of sousveillance with an emphasis on "watchful vigilance from underneath" and a form of surveillance inquiry or legal protection involving the recording, monitoring, study, or analysis of surveillance systems, proponents of surveillance, and possibly also recordings of authority figures. Inverse surveillance is typically undertaken by those who are subjected to surveillance, so it can be thought of as a form of ethnography or ethnomethodology (i.e. an analysis of the surveilled from the perspective of a participant in a society under surveillance). Sousveillance typically involves community-based recording from first person perspectives, without necessarily involving any specific political agenda, whereas inverse surveillance is a form of sousveillance that is typically directed at, or used to collect data to analyze or study, surveillance or its proponents (e.g., the actions of police or protestors at a protest rally).

Inverse surveillance is a type of sousveillance. The more general concept of sousveillance goes beyond just inverse surveillance and the associated twentieth-century political "us versus them" framework for citizens to photograph police, shoppers to photograph shopkeepers, or passengers to photograph taxicab drivers. Howard Rheingold commented in his book Smart Mobs that this is similar to the pedestrian−driver concept, i.e. these are roles that many of us take both sides on, from time to time. Many aspects of sousveillance were examined in the general category of "reciprocal accountability" in David Brin's 1997 non-fiction book The Transparent Society, and also in Brin's novels. The first International Workshop on Inverse Surveillance, IWIS, took place in 2004, chaired by Dr. Jim Gemmell, (MyLifeBits), Joi Ito, Anastasios Venetsanopoulos, and Steve Mann, among others.

Some research has explored why the perpetrators of surveillance are suspicious of sousveillance.

Copwatch is a network of American and Canadian volunteer organizations that "police the police." Copwatch groups usually engage in monitoring of the police, videotaping police activity, and educating the public about police misconduct. Fitwatch is a group that photograph Forward Intelligence Teams (police photographers) in the United Kingdom.

In 2008, Cambridge researchers (in the MESSAGE project) teamed with bicycle couriers to measure and transmit air pollution indicators as they travel the city.

In 2012 the Danish daily newspaper and online title Dagbladet Information crowdmapped the positions of surveillance cameras by encouraging readers to use a free Android and iOS app to photograph and geolocate CCTV cameras.^{[better source needed]}