Headland Archaeology (UK) Ltd undertook a geophysical (magnetometer) survey of land at Thornton Bridge, North Yorkshire, where a new poultry unit is proposed. The survey covered only the development footprint within a larger application area. The survey has not identified any anomalies of definite archaeological potential, mainly identifying anomalies which are consistent with post-medieval and modern land division and drainage. A localised cluster of discrete anomalies within a broad area of increased magnetic response has been identified at the northern end of the proposed access track and may be archaeological in origin, perhaps being due to a spread of magnetically enhanced material, possibly rubble or building material. However, no clear pattern is discernible in the dataset and a modern cause such as tipping/infilling is equally plausible. Therefore, on the basis of the geophysical survey, the archaeological potential over the majority of the development footprint is assessed as very low, and low to moderate in the vicinity of the cluster of discrete anomalies.