St Mary's College C.S.Sp. is a voluntary boys' primary and secondary school run by the Congregation of the Holy Spirit and located in Rathmines, Dublin, Ireland. The school was founded in 1890, closed in 1916, and then reopened in 1926. The school colours are blue and white.

Rathmines is an affluent inner suburb on the Southside of Dublin in Ireland. It begins at the southern side of the Grand Canal and stretches along the Rathmines Road as far as Rathgar to the south, Ranelagh to the east, and Harold's Cross to the west. It is situated in the city's D06 postal district.