Founded in 1030 AD by the Hiberno-Norse king Sitriuc Silkenbeard and Dúnán, first Bishop of Dublin, the originally viking church has been a part of Dublin and Irish history ever since. The wooden viking structure was destroyed during the Norman invasion by king Richard (Strongbow) de Clare, and the stone church was built starting in 1171. Strongbow’s tomb is inside the church walls, and his effigy can be seen just inside the entrance.

Famed saint Laurence O’Toole was named Archbishop in the 1150s and although he died in France in 1180, his heart remains in the cathedral, quite literally. The preserved heart lies inside a heart shaped box enclosed by iron bars, near the back of the church.

A decidedly un-Christian stockade is on display in the crypt (the largest crypt in Ireland or Britain). Made in 1670, these stocks were used to punish criminals in Christ Church Place. They were moved inside the cathedral in 1870.

Another of the cathedral’s more intriguing inhabitants are the mummified remains of a cat and a rat. According to church lore, the cat had chased the rat in to a pipe of an organ and both became stuck. James Joyce used the cat and the rat as a simile in Finnegan’s Wake when he describes someone as being "...As stuck as that cat to that mouse in that tube of that Christchurch organ..." The cat is chasing the rat in perpetuity behind glass in the crypt of the church.