St. Mary's Church is a Roman Catholic church located at 130 Bathurst Street at Portugal Square in the Niagara neighbourhood of Toronto, Ontario, Canada. The parish was established by Irish immigrants in 1852. The Gothic Revival church was designed by Joseph Connolly and completed in 1889, with the tower finished in 1905. It stands as the picturesque western view terminus for Adelaide Street.

Niagara is a neighbourhood in Toronto, Ontario, Canada, located south of Queen Street West; it is usually bordered by Strachan Avenue to the west, Bathurst Street to the east, and the railway corridor to the south, and so named because Niagara Street runs through the centre of it. The eastern portion of this area was first planned as the New Town Extension when Toronto was incorporated as a city. The area was developed as a residential area for the workers of industries located along the CN and CP railway corridors. It remains a working-class neighbourhood that has seen the development of new condominium apartment buildings.