This is a list of notable alleged sightings of unidentified flying objects (UFOs) in the United Kingdom. Many more sightings have become known since the gradual release, between 2008 and 2013, of the Ministry of Defence's UFO sighting reports by the National Archives. In recent years, there have been many sightings of groups of slowly moving lights in the night sky, which can be easily explained as Chinese lanterns. Undertaken between 1997 and 2000, Project Condign concluded that all the investigated sightings of unidentified aerial phenomena in the UK could be attributed to misidentified but explicable objects, or poorly understood natural phenomena.

Project Condign was a secret unidentified flying object (UFO) study undertaken by the British Government's Defence Intelligence Staff (DIS) between 1997 and 2000.