Immaculate Conception Catholic Church is a parish of the Roman Catholic Church in Celina, Ohio, United States. Founded later than many other Catholic parishes in the heavily Catholic region of western Ohio, it owns a complex of buildings constructed in the early 20th century that have been designated historic sites because of their architecture. Leading among them is its massive church, built in the Romanesque Revival style just 43 years after the first Catholic moved into the city: it has been called northwestern Ohio's grandest church building.