Jean-Yves "Blacky" Thériault is a Canadian criminal known for his involvement in organized crime. He gained notoriety in the 1970s and 1980s, particularly in connection with the Mafia in Montreal. Thériault was implicated in various criminal activities, including drug trafficking and extortion. Thériault's life of crime led to multiple arrests and convictions. He became a prominent figure in the underworld, often associated with violence and intimidation. His actions contributed to the ongoing struggles between rival criminal factions in Canada, making him a significant player in the history of organized crime in the region.