File:The Chapel Royal in Dublin Castle (6077218134).jpg

Flash photography is not permitted inside the building.

The Chapel Royal in Dublin Castle was the official Church of Ireland chapel of the Household of the Lord Lieutenant of Ireland.

The foundation stone was laid by the Lord-Lieutenant, John Russell, 6th Duke of Bedford, on 15 February 1807. It was completed behind schedule (the budget also substantially overran) and opened on Christmas Day, 1814, when Charles Whitworth, 1st Earl Whitworth was Lord-Lieutenant.

Lord Whitworth contributed the centre portion of the large stained-glass window above the altar, which he had purchased while in Paris, and which reputedly had come from Russia (he had been plenipotentiary in St. Petersburg in the 1790s). The surroundings are painted glass, executed by a Mr. Bradley in Dublin. At the apex of the window are the arms of Lord Whitworth.

The decoration of the ceiling of the interior was done by George Stapleton (son of Michael Stapleton), a leading stuccodore of the time, while sculptor Edward Smyth (responsible for the "river heads" on the Custom House) and his son John (responsible for the statues on the GPO) carved the larger figures.

Over the chancel window are three life-size figures representing Faith, Hope and Charity. Over the galleries are heads representing Piety and Devotion. All the interior vaulting and columns are cast in timber and feature a paint wash (faux pierre) to give the effect of stone. It was described as having "the most flamboyant and luxurious Dublin interior of its era."

The exterior was clad in a thin layer of "fine limestone from Tullamore quarry", and famously features over 90 carved heads, including those of Brian Boru, St. Patrick, Archbishop Ussher and Jonathan Swift, done by Edward and John Smyth.

The large organ, still playable, is said to have been a gift from Prince Albert, consort of Queen Victoria. The wooden decoration contains a carved head in the centre, which is said to be that of Turlough O'Carolan, the famous Irish composer. As each Lord Lieutenant left office, their coat of arms was carved on the gallery, and then, when space ran out, placed in a window of the chapel. It was noted by Irish nationalists that the last window available was taken up by the man who proved to be the last Lord Lieutenant, Viscount Fitzalan (who was himself a Catholic).

In 1943, the church became the property of the Irish Army, and the former Church of Ireland chapel became a Roman Catholic Church, under the name the Church of the Most Holy Trinity. The Stations of the Cross were then carved by the monks in Glenstall Abbey and presented to the church in 1946. Though it has not been deconsecrated, neither Masses nor Divine Services take place there any more. It has however been recently restored to its nineteenth century state and is open to the public. The crypt is sometimes used for cultural events.