The Shag Harbour UFO Incident took place on the night of October 4, 1967, in the small fishing village of Shag Harbour, Nova Scotia, Canada. Around 11 p.m. on that clear, moonless night, a string of flashing lights was seen descending into the waters off the coast by multiple witnesses, including three RCMP officers, scores of fishermen, and airline pilots. Most witnesses initially thought they were seeing a doomed aircraft.

Witness Laurie Wickens, then 17, driving home with friends, described seeing four lights flashing in a row. Believing it was an airline disaster, he called the local RCMP detachment and reported a large airplane crash, despite being questioned about his sobriety. Several other people also called the Mounties that night, telling the same story. Shortly afterwards, Wickens was among about a dozen people who gathered at the water's edge and watched a glowing, orange sphere, approximately the size of a city bus, bobbing on the waves about 300 metres from shore. At 11:20 p.m., the object slipped beneath the surface silently.

Local authorities and residents quickly began a search, initially thinking it was a plane crash and searching for survivors. No wreckage, bodies, or clues were found. However, volunteer searchers aboard fishing boats soon spotted a long trail of bubbling, yellow foam on the water. A squad of Royal Canadian Navy divers conducted a three-day scan of the harbour floor but also failed to turn up any clues, according to official military records. Laurie Wickens, however, believes the divers did recover something from the water.

UFO researcher Chris Styles later discovered a "trove of government and police records" documenting the incident, making it Canada’s best-documented and most intriguing UFO sighting. These documents, including RCMP reports and military correspondence, contained specific references to unidentified flying objects and made no attempts to explain away what people were reporting. Approximately 36 hours after the sighting, a Defence Department memo was signed stating that authorities had determined the UFO sighting "was not caused by a flare, float, aircraft or in fact any known object". The Canadian government investigated the event but did not arrive at a conclusive explanation.

Chris Styles' subsequent research, including interviews with former military insiders, suggested that the orange orb spotted in Shag Harbour had submerged under its own power and travelled underwater to a location about 50 kilometres north, near Shelburne. This area was the site of a top-secret U.S. military base, disguised as an oceanographic institute, which used underwater devices to track submarines.

The Shag Harbour incident is set apart by its multiple independent and credible witnesses, including law enforcement and airline pilots, and the lack of a dismissive explanation from authorities. While no hard evidence backs theories of Russian submarines or extraterrestrial visitors, the official documentation provides a level of authenticity not often seen in UFO cases. Chris Styles continues his research, stating he is seeking "real answers".

The incident is now often referred to as "Canada's Roswell". The mystery continues to intrigue, and the event is commemorated by the Shag Harbour UFO Incident Society, which operates a museum in the village dedicated to the mystery.