The Celtic Saint, Maelruain, founded a monastery here in the 8th Century. St. Maelruain died in 792 and was buried in Tallaght. In 811 the monastery was attacked and badly damaged by Viking raiders.
St. Maelruain’s Church, at the edge of Tallaght Village, was built in 1829, to replace an older church. The tower of the present St. Maelruain's Church dates from the Medieval period, when it was part of the fortifications of The Pale, which separated the subjects of the Crown within from the native Irish. Tallaght was often raided by the O'Toole and the O'Byrne families and the tower served as a watchpost to give warning against these raids. Tallaght, at that time, was surrounded by a high wall.