The Mont Mégantic Observatory (French: Observatoire du Mont-Mégantic, pronounced [ɔpsɛʁvatwaʁ dy mɔ̃ meɡɑ̃tik]; OMM) is an astronomical observatory owned and operated jointly by the Université de Montréal (UdeM) and the Université Laval (ULaval). 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 Montreal.
The asteroid 4843 Mégantic is named for the observatory.