Tan line

For the Hùng dynasty of Vietnam, see Tân line. For the band, see Tanlines.
A woman at the Iowa State Fair wears a backless dress revealing her swimsuit tan lines

A tan line is a visually clear division on the human skin between an area of pronounced comparative paleness relative to other areas that have been suntanned by exposure to ultraviolet (UV) radiation or by sunless tanning. The source of the radiation may be the sun or artificial UV sources such as tanning lamps. Tan lines are usually an unintentional result of a work environment or recreational activities, but are sometimes intentional. Many people seek to avoid tan lines that will be visible when regular clothes are worn.