Holy Trinity Cathedral, also known as Christ Church, is the oldest of the two medieval cathedrals in the city of Dublin, along with St. Patrick's Cathedral. Since medieval times, it has been the seat of the Archbishop of Dublin, forming part of the Church of Ireland, which is Anglican, and is dedicated to the Trinity.

Its construction dates back to 1030, under the reign of the Viking King Sigtrygg Silkiskegg. Initially, it was a wooden structure located on an elevated site overlooking the Viking settlement of Wood Quay. Subsequently, St. Lawrence O'Toole, the first Irish archbishop in 1152, initiated its enlargement and rebuilding. With Norman control of Ireland, the Norse cathedral was replaced by an Anglo-Norman style cathedral in the period of Archbishop John Cumin.

During the Victorian era, between 1871 and 1878, it underwent significant restoration led by George Edmund Street, which saved parts of the building from collapse but also introduced changes that make it difficult to distinguish the different periods of decoration.

The cathedral has a rich history, including its use at the coronation of Lambert Simnel as "Edward VI" in 1487 and the belief that it contains the tomb of Richard FitzGilbert of Clare, better known as Strongbow, a leader of the Norman invasion. However, some of these historical claims are the subject of debate and controversy.

The cathedral houses the largest cathedral crypt in the British Isles and has recently been refurbished for opening to the public. Among its treasures are historical artifacts, sculptures and a set of candles dating from important events in the cathedral's history.

In addition, the cathedral is known for its bell tower, which has had bells since 1038. Over the centuries, it has undergone damage and renovations, including an accidental explosion in 1603 and an expansion in 1999 that set a world record of 19 bells in use.