The Mont Mégantic Observatory (French: Observatoire du Mont-Mégantic; OMM) is an astronomical observatory owned and operated jointly by the Université de Montréal (UdeM), the Université Laval (ULaval), and McGill University. Founded in 1978, the observatory houses the second largest telescope in Eastern Canada after David Dunlap Observatory near Toronto. It is situated at the summit of Mont Mégantic, the highest point of Eastern Canada accessible by car. OMM is about 60 kilometres (37 mi) east of Sherbrooke and 190 kilometres (120 mi) east of Montréal.

The asteroid 4843 Mégantic is named for the observatory.

Telescope

The 1.6 metres (63 in) Ritchey-Chrétien telescope is equipped with a complement of modern instruments. Imaging, spectroscopy, and polarimetry are routinely conducted at both visible and infrared wavelengths.

Light pollution

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).

Mont Mégantic is a monadnock located in Québec, Canada, about 15 km north of the border between Québec and the U.S. states of Maine and New Hampshire. Mégantic is on the border of the regional county municipalities of Le Granit and Le Haut-Saint-François. Its summit is the highest point of the latter. Many geologists believe that Mont Mégantic is a member of the Monteregian Hills formed by the New England hotspot, as it has the same mechanism and depth of intrusion.

Mont Mégantic stands within the watershed of the Saint Lawrence River, which drains into the Gulf of Saint Lawrence. The east side of Mégantic drains into Rivière Victoria, thence into Lac Mégantic, the Chaudière River, and the St. Lawrence. The rest of Mégantic drains into Rivière Au Saumon (Salmon River), thence into the Saint-François River, and the St. Lawrence.

Observatoire du Mont Mégantic (OMM) is located on the mountain's summit, which is the highest point in Québec accessible by road. The mountain is in the middle of the 55 km² Parc national du Mont-Mégantic. The annual Tour de Beauce bicycle race is routed over Mont Mégantic.