This is a list of important sightings of unidentified flying objects (UFOs), some of which include claims about close encounters where people see strange things or feel something happen, or reports of being taken by aliens. UFOs are generally described as any strange things seen in the sky that cannot be quickly explained. After checking, most UFOs are found to be known objects or natural events in the sky, while a few remain unexplained. UFOs have been called by many names, such as "flying saucer" and "unidentified anomalous phenomena" (UAP). Sometimes, "UAP" is used to avoid linking the topic to ideas about secret plans or conspiracies.

Although UFO sightings are often seen as unusual, they happen often. In 1947, the first wave in the United States had over 800 sightings reported in newspapers. In the United Kingdom, the government receives hundreds of reports each year. In Brazil, pilots alone report dozens of sightings every year. Some sightings become important in culture, based on what people believe and the technology of that time.

20th century

Gordon Cooper, one of the first astronauts in Project Mercury, saw a metallic object without wings flying over Germany in the 1950s. At first, he thought the object was a Soviet airplane. His opinion changed after an event at Edwards Air Force Base. Cooper sent James Bittick and Jack Gettys, who knew about experimental aircraft, to a dry lakebed to set up equipment for recording data with photographs. The men returned shaken and described seeing a wingless aircraft with retractable legs silently land and take off near them. Cooper reported the event to The Pentagon, which requested all photographs of the object. Cooper examined the photos before sending them and believed the government hid evidence of a UFO encounter.

By location

The lists below include UFO reports discussed earlier, as well as other UFO reports from certain places.