Dún Aonghasa (unofficial anglicised version Dun Aengus[2]) is the best-known of several prehistoric hill forts on the Aran Islands of County Galway, Ireland.

[7] Its name, meaning 'Fort of Aonghas', may refer to the pre-Christian god of the same name described in Irish mythology, or the mythical king, Aonghus mac Úmhór.

The fort consists of a series of four concentric walls of dry stone construction, built on a high cliff some one hundred metres above the sea.

Impressively large among prehistoric ruins, the outermost wall of Dún Aonghasa encloses an area of approximately 6 hectares (14 acres).

Also in the vicinity is a Neolithic tomb and a small heritage park featuring examples of a traditional thatched cottage and a poteen distillery.