Saint-Pierre-de-PlesguenSaint-Pierre-de-Plesguen is a former commune in the Ille-et-Vilaine department in Brittany in northwestern France. On 1 January 2019, it was merged into the new commune Mesnil-Roc'h.WWW saintpierredeplesguen.frPersonalitiesHughes Felicité Robert de Lamennais lived in Saint-Pierre-de-Plesguen during the 19th century.PopulationInhabitants of Saint-Pierre-de-Plesguen are called saint-pierrais in French.