Coordinates: 45°27′20.66″N 71°9′9.81″W / 45.4557389°N 71.152725°W / 45.4557389; -71.152725

The Observatoire du Mont-Mégantic (abbreviated as OMM and called Mont Mégantic Observatory in English) is an astronomical observatory owned and operated jointly by the Université de Montréal, the Université Laval and the McGill University. Founded in 1978, it is the largest observatory of eastern Canada, and is situated at the summit of Mont Mégantic, the highest point of the province of Québec to be accessible by car.

The observatory (IAU code 301) is about 250 km east of Montréal.

The telescope is equipped with a complement of modern instruments: visible imagery, spectroscopy and polarimetry are routinely conducted. There is also an infrared imager, but it is often "borrowed" by astronomers observing at the Canada-France-Hawaii Telescope (CFHT).

The current director is René Doyon.

Efforts to control local light pollution (about one-quarter of which is due to the nearby city of Sherbrooke) have led to the establishment of the world's first International Dark-Sky Association (IDA) Dark Sky preserve around the observatory, covering some 5500 square km (2123 square miles).

The Asteroid 4843 Mégantic is named for the Observatory