the practice of going without clothes, generally for reasons of health or comfort. Nudism is a social practice in which the sexes interact freely but commonly without engaging in sexual activities.

The origin of the practice in Germany in the early 20th century coincided with a rebellion against the rigid moral attitudes of the late 19th century. The first known nudist club, Freilichtpark (“Free Light Park”), appeared about 1903 near Hamburg and was soon followed by Richard Ungewitter's seminal work Die Nacktheit (1906; Nakedness), which went through several printings. Nudism spread through Europe after World War I and became established in North America during the 1930s. The American League of Physical Culture was founded in 1929 to promote nudism. In the United States and Canada the practice has remained restricted to a few secluded camps and beaches. The atmosphere of these camps is generally deliberately nonerotic, and most are governed by strict rules of conduct.

Although public nudity of varying degrees became increasingly common in the latter part of the 20th century, nudism still is not widely accepted. Most nudists are adults, although families sometimes participate. Adults who practice nudism have been found to be psychologically healthy, but the impact of nudism on children is a subject of dispute among psychologists.