| Barn at Trewyn Farm | |
| Type: | Barn |
| Map Relief: | yes |
| Coordinates: | 51.8992°N -2.9799°W |
| Location: | Llanvihangel Crucorney, Monmouthshire |
| Built: | 16th century |
| Architecture: | Vernacular |
| Governing Body: | Privately owned |
| Designation1: | Grade II* listed building |
| Designation1 Offname: | Barn at Trewyn Farm |
| Designation1 Date: | 29 January 1998 |
| Designation1 Number: | 19246 |
| Designation2: | Grade II listed building |
| Designation2 Offname: | Old Farmhouse at Trewyn Farm |
| Designation2 Date: | 29 January 1998 |
| Designation2 Number: | 19247 |
| Designation3: | Grade II listed building |
| Designation3 Offname: | Trewyn Farmhouse |
| Designation3 Date: | 29 January 1998 |
| Designation3 Number: | 19248 |
The barn at Trewyn Farm, Llanvihangel Crucorney, Monmouthshire is part of a complex of farm buildings dating from the late 16th century. The barn has a Grade II* listing, with the Old farmhouse at Trewyn Farm and Trewyn Farmhouse having separate Grade II listings.
The old farmhouse at Trewyn is an early 16th century hall house. Refurbished in the 19th century, it is largely unaltered since that date. Constructed of Old Red Sandstone rubble the interior roof timbers are heavily smoke-blackened, indicating the presence of an open hearth at the time of its original construction. In the late 17th century, possibly as late as 1700, the new farmhouse was built across the farmyard. Reconstructed in the Victorian era, the building is of three-storeys and of cement rendered sandstone rubble. Both the old and the new farmhouses have Grade II listings. The barn is, architecturally, the most important element of the farmstead which is reflected in its Grade II* listing. Dating originally from the 16th century, it was extended in the 17th. It has four cruck trusses although the present roof is of corrugated iron dating from the 20th century. Cadw describes it as "an unusually good cruck barn".