The 12th Century preserved heart of the Patron Saint of Dublin, Saint Laurence O'Toole, has been stolen from Christ Church Cathedral.
His heart was preserved since the 13th century and has been a major pilgrimage site
The Cathedral was opened at 9.30am, to no alarm activation and no sign of any break-in.
The heart was believed to be stolen between last night and noon today.
The Heart of St Laurence O'Toole was kept in a wooden heart shaped container sealed within a small iron barred box.
The one time Archbishop St Laurence O'Toole was born Lorcán Ua Tuathail in Castledermot, Co Kildare in 1128 and known as Laurence O'Toole, died November 1180 in Normandy France.
His heart was preserved in Christ Church Cathedral since the 13th century and has been a major pilgrimage site since the medieval period until the present day.
The Dean of Christ Church Cathedral and the diocese of Dublin and Glendalough, the Most Reverend Dermot Dunne stated "I am devastated that one of the treasured artifacts of the cathedral is stolen.
It has no economic value but it is a priceless treasure that links our present foundation with its founding father, St Laurence O'Toole."
Gardaí wish to speak to anyone who may have visited Saint Lauds Chapel in Christ Church Cathedral between yesterday evening and today at 12.30pm and seen anything unusual or suspicious in the Chapel, Cathedral.
Anyone in a position to assist with the investigation are asked to contact them at Kevin Street at 01- 6669400, the Garda Confidential Telephone Line 1800 666 111 or any Garda Station.