Saint-Théophile is a municipality in the Municipalité régionale de comté de Beauce-Sartigan in Quebec, Canada on the Canada–United States border. It is part of the Chaudière-Appalaches region and the population is 702 as of 2021. It is named after reverend Théophile Montminy, who had been chosen by the archdiocese to find a proper location for a church. Saint-Théophile lies next to the border with Maine, and there is a border crossing on Route 173 within the municipality, in the hamlet of Armstrong. The Armstrong custom office is the third in importance in Quebec.