The longstanding collaboration between Aalto and the Church has previously been put down to reciprocal expediency, and the buildings perceived as spatially stirring, yet devoid of religious meaning. By analysing designs for churches, parish centres, funerary chapels and cemeteries in Finland, Denmark, Germany and Italy, this book instead reveals that Aalto's engagement with religion transcended artistic opportunism. Through a detailed analysis of the religious actors and factors that shaped the design and construction of Aalto's sacred works, as well as of previously uncovered archival material, it shows that religious influences were intrinsic and intimately related to it. The resultant buildings neither glorify nor deny institutional religion -- instead, this book argues, they challenge rigid dogmatism in religion as much as in modern architecture.