A flying saucer (also referred to as a flying disc) is a type of unidentified flying object (UFO) with a disc- or saucer-shaped body, usually described as silver or metallic, occasionally reported as covered with running lights or surrounded with a glowing light, hovering or moving rapidly either alone or in tight formations with other similar craft, and exhibiting high maneuverability.

Although disc-shaped flying objects have been interpreted as recorded occasionally since the Middle Ages, the first highly publicized sighting by Kenneth Arnold on June 24, 1947, resulted in the creation of the term by U.S. newspapers. Although Arnold never specifically used the term "flying saucer", he was quoted at the time saying the shape of the objects he saw was like a "saucer", "disc", or "pie-plate", and several years later added he had also said "the objects moved like saucers skipping across the water." (The Arnold article has a selection of newspaper quotes.) Both the terms flying saucer and flying disc were used commonly and interchangeably in the media until the early 1950s.

Arnold's sighting was followed by thousands of similar sightings across the world. Such sightings were once very common, to such an extent that "flying saucer" was a synonym for UFO through the 1960s before it began to fall out of favor. However, the term is still often used generically for any UFO.

More recently, the flying saucer has been largely supplanted by other alleged UFO-related vehicles, such as the black triangle. The term UFO was, in fact, invented in 1952, to try to reflect the wider diversity of shapes being seen. However, unknown saucer-like objects are still reported, such as in the widely-publicized 2006 sighting over Chicago-O'Hare airport.

Many of the alleged flying saucer photographs of the era are now believed to be hoaxes. The flying saucer is now considered largely an icon of the 1950s and of B-movies in particular, and is a popular subject in comic science fiction.