Croaghaun (Irish: Cruachán) is a mountain on Achill Island in County Mayo, Ireland.

They are part of a sequence of sheer rock faces which start south of Keem Bay and loop around the uninhabited north-west of the island, by Achill Head and Saddle Head, and east to Slievemore, occasionally dropping vertically into the waters of the Atlantic Ocean.

September and October are the best time to see the fastest creatures on Earth here, as they teach their young to fly.

Metamorphic, quartz-laden gems may be observed, along with Mediterranean heathers and the waters of the Atlantic.

It is common to see schools of bottlenose dolphins and basking sharks, once a source of revenue for Achill Island (BBC, 2009).