Personal space is the region surrounding each person, which if entered by another person without this being desired physical intimacy, makes them feel uncomfortable. It may be due to the limited available space, different standards, or rudeness.

What distance is appropriate for a particular social situation depends on culture. It is also a matter of personal preference. People may feel uncomfortable if the distance is too large (cold) or too small (intrusive).

Personal space is highly variable. Those who live in a densely populated environment tend to have smaller personal space requirements. Thus a resident of Hong Kong would have a smaller personal space that someone who is home on the Mongolian steppe. See also ethnic stereotype.

It can also be heavily affected by a person's position in society, with the more affluent a person being the larger personal space they demand.

While it is highly variable and difficult to measure accurately the best estimates place it at about sixty centimeters on either side, seventy centimeters in front and forty behind for an average westerner.

In certain circumstances people can accept having their personal space violated. For instance in romantic encounters the stress from violated personal space can be redirected into emotional fervour. Another method of dealing with violated personal space, according to psychologist Robert Summer , is dehumanization. He argues that, for instance on the subway, crowded people imagine those infiltrating their personal space as inanimate.

Attitudes of people regarding someone else entering their personal space may depend on the sex of both people. Some train cars are women-only, to allow women to avoid men entering their personal space, and groping them.

See also proxemics.