Penarth Fawr

Penarth Fawr (also spelled Pennarth and historically Pennardd) is a hall house in the community of Llanystumdwy, Gwynedd, Wales.

The west wing of Penarth Fawr is significant as a surviving example of a medieval hall house. It was built c. 1476 by Hywel ap Madog, a member of a prominent Eifionydd family, and originally consisted of a three-bay hall with a one-bay service end to the south and a parlour wing to the north. It was later altered, but restored to approximately its medieval appearance in 1937; the intact roof structure, which includes a spere truss, is particularly notable. The hall is described as "one of the most important medieval gentry houses to survive in Wales" by Cadw, the historic environment service of the Welsh Government, and as "an important medieval hall house" in the Buildings of Wales series. It is a grade I listed building and a scheduled monument. The hall passed into state care in 1949 and is now managed by Cadw.

There is a seventeenth-century wing attached to the south-east of the building, which is a private dwelling. A parlour wing of the same date to the north of the hall, which replaced its medieval predecessor, was demolished c. 1843. The seventeenth-century wing and nearby stables are each listed at grade II.