Unsolved Mysteries is an American mystery documentary television series, created by John Cosgrove and Terry Dunn Meurer. Documenting cold cases and paranormal phenomena, it began as a series of seven specials, presented by Raymond Burr, Karl Malden, and Robert Stack, beginning on NBC on January 20, 1987, becoming a full-fledged series on October 5, 1988, hosted by Stack. After nine seasons on NBC, the series moved to CBS for its 10th season on November 13, 1997. After adding Virginia Madsen as a co-host during season 11 failed to boost slipping ratings, CBS canceled the series after only a two-season, 12-episode run on June 11, 1999. The series was revived by Lifetime in 2000, with season 12 beginning on July 2, 2001. Unsolved Mysteries aired 103 episodes on Lifetime, before ending on September 20, 2002, an end that coincided with Stack's illness and eventual death.

After a six-year absence, the series was resurrected by Spike in 2007, and began airing on October 13, 2008. This new, revived version was hosted by Dennis Farina, who mainly tied together repackaged segments from the original episodes. Farina hosted 175 episodes before the series ended again on April 27, 2010. Cosgrove-Meurer Productions maintains a website for the show, featuring popular accounts and ongoing cold cases (murder or missing persons), with a link to an online form should a viewer have information on an unsolved crime. As of 2017, the show maintains a YouTube page where viewers can submit their own mysteries. If accepted, Unsolved Mysteries posts a video of the viewer describing the mystery. That same year, FilmRise acquired worldwide digital distribution rights to the series and announced its intent to release updated versions of its episodes. These shows are currently streaming on Amazon Prime, Tubi TV, and on its own dedicated channel on Pluto TV in the United States and the United Kingdom. Since February 2017, the Spike episodes have been officially posted on YouTube, split into eight seasons. In July 2017, the series began streaming on Hulu in the United States. Between February and March 2019, FilmRise began posting digitally restored and re-edited episodes, hosted by Stack, on YouTube.

On June 22, 2018, Terror Vision Records released the official soundtrack for the series. In 2017, the show's creators expressed interest in reviving the series. On January 18, 2019, Netflix picked up a reboot of the series which premiered on July 1, 2020. The first season of the reboot was split into two volumes containing six episodes each. In September 2022, Netflix announced that a third volume of new episodes would begin streaming in October 2022. In February 2024, it was announced that a fourth volume would begin streaming in 2024. It was confirmed that the fourth volume would begin streaming in July 2024. A fifth volume, consisting of four episodes, was announced on July 31, 2024. It began streaming in October the same year.