The stone circles in the British Isles and Brittany are a megalithic tradition of monuments consisting of standing stones arranged in rings. These were constructed from 3300 to 900 BCE in Britain, Ireland and Brittany. It has been estimated that around 4,000 of these monuments were originally constructed in this part of north-western Europe during this period

Around 1,300 of them are recorded, the others having been destroyed. Although stone circles have been erected throughout history by a variety of societies and for a variety of reasons, in the Late Neolithic and Early Bronze Ages, this particular tradition was limited to the British Isles and the neighbouring area of

continental Europe now known as Brittany. The rings were not distributed equally across this area, but were concentrated in several highland regions: north-eastern and central Scotland, the Lake District, the south-west peninsula of England, and the north and south-west of Ireland. Sparser groupings can also be found in Caithness, the Outer Hebrides, the Peak District, the Wicklow Mountains, Wales and Wessex.

Their original purpose is not fully known, but archaeological investigation has shed some light on it. It is widely thought that they served a ritual or ceremonial purpose, particularly in relation to solar and/or lunar alignments. In a minority of cases, some were also used as cemeteries, with burials being made in and around the circle.

Antiquarian investigation into the circles began in the Early Modern period, intensifying after the publications of notable English antiquarian William Stukeley in the 18th century. At the time, scholars understood little of prehistoric Britain, with the megalithic circles typically being ascribed either to the druids of the Iron Age or to the Danish settlers of Early Medieval times.