The Eddystone, or the Eddystone Rocks, are a seaswept and heavily eroded group of rocks some 9 statute miles (14 kilometres) southwest of Rame Head in Cornwall, England, United Kingdom. Formerly a treacherous hazard for ships in the approaches to the English Channel and the port city of Plymouth, the rocks have played host to four iterations of the Eddystone Lighthouse, and are still home to the current lighthouse and the stub of its immediate predecessor.
There have been four lighthouses on the Eddystone Rocks. Winstanley (two versions; the second however just replaced the top of the structure), Rudyard, Smeaton and finally the Douglass Lighthouse, which is the present one. When the Douglass Lighthouse was completed the people of Plymouth, grateful for the countless lives which had been saved since the introduction of the lighthouses, paid for the dismantling of the Smeaton Lighthouse from the red rocks of Eddystone and reassembly at Plymouth Hoe, where it is a popular tourist attraction today.
A traditional sea-shanty "The Eddystone Light" chronicles a fictional encounter between the lighthouse keeper and a mermaid. The Seekers, the Weavers, and Peter, Paul and Mary have recorded the shanty.
Eddystone rock is something of an anomaly in the geology of the South West region; it is composed of garnetiferous gneissic rock which is part of a considerable underwater outcrop of mica-schists and granitoid gneisses which have not been found elsewhere in South West England.
Isotopic ages suggest that the last period of deformation was during the end of the Devonian, but their highly metamorphosed state indicates they likely have an older ancestry, a relic of earlier tectonic activity, probably of Precambrian age.