Hillforts in Britain refers to the various hillforts within the island of Great Britain. Although the earliest such constructs fitting this description come from the Neolithic period, with a few also dating to the later Bronze Age, British hill forts were primarily constructed during the Iron Age. Some of these were apparently abandoned in the southern areas that were a part of Roman Britain, although at the same time, those areas of northern Britain that remained free from Roman occupation saw an increase in their construction. Some hillforts were reused in the Early Medieval period, and in some rarer cases, into the Later Medieval period as well. By the Early Modern period these had essentially all been abandoned, with many being excavated by archaeologists in the nineteenth century onward.
There are around 3,300 structures that can be classed as hillforts or similar "defended enclosures" within Britain. Most of these are clustered in certain regions: south and south-west England, the west coast of Wales and Scotland, the Welsh marches and the Scottish border hills. British hillforts varied in size, with the majority covering an area of less than 1 ha (3 acres), but with most others ranging from this up to around 12 ha (30 acres) in size. In certain rare cases, they were bigger, with a few examples being over 80 ha (200 acres) in size.
Various archaeologists operating in Britain have criticised the use of the term "hillfort" both because of its perceived connection to fortifications and warfare and because not all such sites were actually located on hills. Leslie Alcock believed that the term "enclosed places" was more accurate, whilst J. Forde-Johnston commented on his preference for "defensive enclosures".
British hillforts, as now recognised, first appeared in the Late Bronze Age. Archaeologists Sue Hamilton and John Manley believed they were a part of "...substantial landscape and social reconfigurations at the start of the first millennium [BCE]", that coincided with the change of three characteristics of British Bronze Age society: "...disappearance of an archaeologically visible burial rite, ... increased deposition of prestige metalwork in rivers, ... and the demise of a middle Bronze Age settlement format of groups of round houses set within enclosures." They went on to note that "Accrued place-value may have been important in the establishment of the earliest hillforts. These are often in locations with conspicuous traces of previous ritual monuments. This may have been a means of validating new social practices through making links with the past". This idea was examined in more depth by ethnologist J. Forde-Johnston, who made note of how a number of Iron Age hillforts had been built close to earlier Bronze Age barrows. Commenting on the fact that both types of monument typically were constructed in high locations, he said, "It is not surprising that the two features should coincide in several dozen cases." He added that it was possible that hillforts had been intentionally sited near barrows for defensive protection from the "...sacred associations of the burial place."