St. Assam's is the name of two historic churches in the village of Raheny, Dublin, one a picturesque ruin in the middle of the village, one the structurally sound but no longer primary church built for the local Roman Catholic community of the area after the revival of religious rights. Both buildings lie within the area of the ráth (ring fort) which gave the village and district its name, and which was perhaps 110 m across.
There was settlement in the Raheny area dating back to at least Celtic times, and it is believed a Christian establishment back to early Christian times in Ireland. The Parish of Raheny was erected in the 12th century, not later than 1152, probably initially in the Archdiocese of Glendalough and then in the Fingal Deanery of the Diocese of Dublin, and almost certainly had had a church for many years by then.
The first surviving reference to a church building in the area dates from 1189, in a Papal Bull of Clement. The Chapel of Raheny is mentioned again in a concession of the Archbishop of Dublin (1372) and a will (John Sheriff, 1472), which left money "for the care of the churches of Raheny, Coolock and Little Grange." No specific church name is given in any of these documents.
From a reference in the Parliamentary Gazetteer to 1609, the older of the current churches may have been standing in some form. Whatever building was there, the regal visitation report of 1615 for north County Dublin references it, with repairs due to the chancel. By this period of the early 17th century, the church was almost certainly operating within the State church, the Church of Ireland, albeit most of the population were Catholic, probably worshipping in houses, or perhaps at Coolock or Artaine (see Parish of Coolock (Roman Catholic).
The now-ruined Church of St. Assam, locally known as "the old Protestant church", was rebuilt in 1712 on the site of "the parochial church dedicated to St. Assam", according to a dedication stone in the wall. It was a simple structure, 16.25 m by 7.15 m externally (with walls 0.75 m thick), and a mid-19th century plan shows a porch at the west end and a vestry at the east end of the north side, with internal arrangements for 116 worshippers. The porch is described in the Parliamentary Gazetteer as having a flat bell turret while the still-high east gable had a large window with tracery. Rectangular sockets on the walls may have been used to hold wooden panelling prior to the closure of the church in 1889, following the building of All Saints Church a few hundred metres citywards.