Gloddaeth Hall originated as a large country house in Llandudno, Conwy, Wales. It is designated by Cadw as a Grade I listed building. It stands on land which had been owned by the Mostyn family since the 15th century. The core of the building is a sixteenth century hall and two storey solar block, built of stone rubble with freestone dressings. There are gabled stone slate roofs. The hall is open to the hammer beam roof. The lower room of the solar has sixteenth century panelling, the upper seventeenth century panelling. A wing to the east was added around 1700.
In the 19th century, further additions were made to the building by William Nesfield, and by John Douglas, who designed a new west wing for Augusta, Lady Mostyn in 1889. The hall now forms part of St David's College.
The hall now forms part of St David's College, a mixed sex independent boarding and day school, which caters to pupils aged 9–19.