This is the first comprehensive study of St Fagans Castle, an Elizabethan country house in Cardiff which is of twofold significance as a Grade I-listed building, and home to St Fagans National Museum of History since 1948. The house was built by a local lawyer named Dr John Gibbon in about 1580, and was one of the first symmetrical country houses in Wales influenced by the Italian Renaissance. This study takes a multi-period and cross-disciplinary approach to telling the story of St Fagans, with chapters spanning the twelfth to the twentieth century, and interrelated sections on architectural history, garden history and ownership. Key themes explored in the work include the impact of the Italian Renaissance on country houses in Wales; the architectural distinction of country houses in Wales, especially in comparison with English country houses; the contribution of women to architectural and garden developments at St Fagans; and the colonial connection at St Fagans.