Chûn Castle is a large Iron Age hillfort (ringfort) near Penzance in Cornwall, England, United Kingdom.

[1] The fort was built about 2,500 years ago, and fell into disuse until the early centuries AD when it was possibly re-occupied to protect the nearby tin mines.

Edward Lluyd made a plan of this fort in around 1700, remarking that its structure and security showed "military knowledge superior to that of any other works of this kind which I have seen in Cornwall".

The remains today are still clearly visible, even though the once twenty-feet-odd walls now stand at around five feet, due to its use in the 19th century as a quarry for buildings in Penzance and Madron.

[4] At the 1886 annual meeting of the Penzance Natural History and Antiquarian Society, concern was shown for the removal of stone from here, as well as Kenidjack Castle and Madron Well.