(Congregatio Sancti Spiritus) 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 (from 1917 until 1926 the St. Mary's operated as a House of Philosophy for the Spiritans, before it moved to Blackrock.).

The following schools were also founded by the Holy Ghost Fathers in Ireland: Saint Mary's College C.S.Sp.

is directly associated with the St. Mary's College Rugby Club located in Templeogue.

The club has been home to some of Leinster and Ireland's greatest rugby players.