Swinging, sometimes referred to as the swinging lifestyle or simply the lifestyle, includes a wide range of sexual activities conducted between three or more people. Swinging activities can include watching others have sex, having sex with your partner while being watched (both are termed 'soft' swinging', or exchanging partners and having sex (which is the most common definition).

Typically swinging activities occur when a married, or otherwise committed, couple engages in the abovementioned activies with a similar couple or a single male(s), female(s) or both. These acts may or may not occur in the same room and may or may not include bisexual interaction, the latter most common among female participants. Sexual contact between males is less prevalent, though still an element in swinging.

Some 'lifestyle' activities are highly organized. Most major cities have at least one major swing club in a permanent location. These clubs often keep a low profile to avoid negative attention. Swingers also meet through lifestyle magazines, personal ads, swinging house parties, and the Internet.

Some swingers consider the Lifestyle to be a distinct subculture. A generally recognized rule of the swinging lifestyle is "No means no" signifying that rejection of a sexual proposal does not require justification and must always be respected.

According to Terry Gould's The Lifestyle: A Look at the Erotic Rites of Swingers (ISBN 1552094820), swinging began among U.S. Air Force pilots and their wives during World War II.

The random partner swapping "key party" depicted in Ang Lee's film The Ice Storm may actually be a Hollywood invention. "Key party" is sometimes used in swinging circles, but it refers to an invitational event.

See also group sex.