The outage started at about 3:30 p.m. ET.
According to Hydro-Québec's website, at 4 p,m. more than 85,000 homes and businesses on the island of Montreal have no electricity.
In Laval, more than 37,000 Hydro-Québec clients lost power.
In the Laurentians and the Montéregie, roughly 55,000 customers were in the dark.
Police officers were stationed across the city signalling traffic, as many traffic lights are out.
Hydro-Quebec tweeted that the problem was related to two lines on the transmission grid.
In some areas, power has begun to be restored.
As of 4:45 p.m., the number of homes and businesses without power dropped to 50,000.