Built between 1884 and 1887, Saint-Antoine-de-Padoue is a Roman Catholic Victorian Neo-Gothic church situated in the heart of Vieux-Longueuil, on the south-shore of Montreal. Saint-Antoine-de-Padoue co-Cathedral has never been studied in depth and no significant research explaining the church's architectural importance in terms of style, decoration, liturgical functions and cultural identity has ever been published until this date. The thesis will demonstrate that Saint-Antoine-de-Padoue co-Cathedral's architectural style evokes its cultural history, illustrates Catholic ideals, beliefs and hopes, and forms its cultural identity. I will argue that the choice of the church's architectural style is not only appropriate to the main artistic trends of the period, but that it also reflects the church's historical reality composed of both French and English cultures. Furthermore, I will assert that Saint-Antoine-de-Padoue co-Cathedral's Neo-Gothic architecture suits perfectly a Catholic church's liturgical functions and allows a prayerful and meditative atmosphere. I intend to answer my thesis question by considering the relationship between Longueuil's co-cathedral and the theories on religious architecture offered by Augustus Welby Northmore Pugin (1812.1852) and the Cambridge Camden Society (founded in 1839), thereby placing the structure in an aesthetic, historical and theoretical context