Saint-Léonard-d'Aston is a municipality in Nicolet-Yamaska RCM in the Centre-du-Québec region of Quebec, Canada. The population as of the Canada 2011 Census was 2,271. The municipality is situated along Route 155, partway between Drummondville and Trois-Rivières. Autoroute 20 and a major intercity railway line operated by Via Rail also cross through the town.