Eaton Socon Castle stood beside the River Ouse in the village of Eaton Socon, which was originally a village in Bedfordshire but is now a district of St Neots.

The castle was a Norman double enclosure, whose construction required the demolition of Saxon houses, and was surrounded by moats filled with water diverted from the river. It was once in possession of the de Mandeville family but by 1156 was held by the Beauchamp family. Only earthworks now remain and can be seen from the river or on aerial maps.