An oval barrow is a mound of earth and/or stones of roughly elliptical plan covering or containing one or more human burials and/or other ceremonially placed deposits, sometimes partly or wholly surrounded by a ditch from which the material to build the mound was derived. Oval barrows are generally less than 45m long and tend to be about half as broad as their length. Well preserved examples survive as earthworks up to 3m high, but when heavily denuded only the ditches and bedrock cut components may remain.

Oval barrows are often confused with other classes of monument, especially long barrows and long mortuary enclosures. In both cases the more ellipsoid plan and smaller size of oval barrows provide the main means of differentiation, although attention should also be given to position and associations. Other possible confusions arise with conjoined bowl barrows, which can usually be distinguished by their "hour-glass" shaped ditch, and, where only cropmark evidence survives, with pillow mounds, clamps for root crops, and glacial features.

Specifically excluded from the definition of oval barrows are small long barrows with a distinctively rectangular or trapezoidal form, and simple passage graves with two of more chambers set back-to-back in a slightly oval rather than circular mound.

Oval barrows appear to have been burial monuments, although some, if not all of them may also have served as ritual and ceremonial foci. As such, the function of oval barrows undoubtedly overlaps with that of other classes of monument.