A class of middle Neolithic burial monument found extensively across the British Isles and related to other contemporary tomb‐building traditions in other parts of northwestern Europe, especially northern France. The essential features of a long barrow are the long rectangular or trapezoidal mound of soil and stone, sometimes edged with a peristalith, a dry‐stone wall, or timber posts; flanking ditches or quarry pits from which the material to construct the mound was obtained; chambers within the mound built either of orthostats or timber; and some kind of elaboration to the higher and broader end of the mound in the form of a concave forecourt or façade. Much literature on the period distinguishes between so‐called earthen long barrows in the southern and eastern part of the country (sometimes mistakenly called unchambered long barrows because they have chambers of timber rather than stone) and the stone chambered tombs of the north and west. Both are part of the same tradition of long‐barrow building, although not all chambered tombs are long barrows (some are passage graves, portal dolmens, etc.).
The chambers within long barrows are located in one of two areas: terminal chambers that open into the mound form the wider higher end of the barrow, from the back of the forecourt or centre of the façade; or lateral chambers that open into the side of the mound. In all cases the chambers represent a small proportion of the overall structure, prompting speculation that the barrows may also have served as territorial markers. The burials are usually disarticulated inhumations, the corpses having been placed in the entrance areas to the chambers and then, bit by bit, moved further into the mound as they decayed and space was needed for the introduction of new burials.
All dated long barrows were built and used during the mid 4th millennium bc; many show signs of abandonment and in some cases deliberate blocking after about 3000 bc. A number of regional groupings can be recognized on the basis of concentrations in the distribution and the use of particular architectural details, including Cotswold–Severn tombs, Clyde tombs, Carlingford tombs, Wessex long barrows, Yorkshire long barrows, Medway tombs, East Anglian and Midland group; and East Scottish group.