Fieldstone is a building construction material. Strictly speaking, it is stone collected from the surface of fields where it occurs naturally. Collections of fieldstones which have been removed from arable land or pasture to allow for more effective agriculture are called clearance cairns.

In practice, fieldstone is any architectural stone used in its natural shape and can be applied to stones recovered from the topsoil or subsoil. Although fieldstone is generally used to describe such material when used for exterior walls, it has come to include its use in other ways including garden features and interiors. It is sometimes cut or split for use in architecture.