The Ring of Brodgar (or Brogar) is a Neolithic henge and stone circle in Orkney, Scotland. The ring of stones stands on a small isthmus between the Lochs of Stenness and Harray. The centre of the circle has never been excavated by archaeologists and scientifically dated; the monument's age remains uncertain. However, it is generally thought to have been erected between 2500 BC and 2000 BC, and was, therefore, the last of the great Neolithic monuments built on the Ness.

The circle is 104 metres in diameter, and the third largest in the British Isles. The henge originally comprised 60 stones, of which only 27 remained standing at the end of the 20th century. The stones are set within a circular ditch up to 3 metres deep and 9 metres wide that was carved out of the solid bedrock by the ancient residents.

The surrounding area is full of other standing stones and round piles of earth atop prehistoric tombs, making a significant ritual landscape. Although its exact purpose is not known, the proximity of the Standing Stones of Stenness and its Maeshowe tomb make the Ring of Brodgar a site of major importance. A scheduled ancient monument, the Ring of Brodgar was inscribed by UNESCO part of the "Heart of Neolithic Orkney" World Heritage Site in 1999.

Excavations by Orkney College at the nearby Ness of Brodgar site between the Ring and the Stones of Stenness have uncovered several buildings, both ritual and domestic and the works suggest there are likely to be more in the vicinity. Pottery, bones, stone tools and a polished stone mace head have also been discovered. Perhaps the most important find is the remains of a large stone wall which may have been 100 metres long and up to 6 metres wide. It appears to traverse the entire peninsula the site is on and may have been a symbolic barrier between the ritual landscape of the Ring and the mundane world around it.