Phallic imagery occurred throughout the Roman world and is most commonly found on small portable items such as amulets and pendants, and on buildings and structures. This paper details three Romano-British instances of phallic carvings found on millstones and one on a rotary quern. It assesses the style and positioning of the carvings in relation to the functional operation of the stones, reviews their contexts of recovery geographically and chronologically and considers the likely symbolism and meaning of the carvings.