Rushen parish includes the southwestern extremity of the island, together with the Calf of Man, along with its rocky outcrops Kitterland and Chicken Rock, and encompasses an area of about 10 square miles (26 km2).

It stretches along the coast from Strandhall (located about halfway between Castletown and Port St Mary) to the precipices west of Cronk ny Irrey Laa (Hill of the Day Watch, also spelled Arrey), known as the Stacks or the Slogh, covering a distance of 16 miles (26 km).

The west of the parish is hilly, extending southwards from Cronk ny Irrey Laa (437 metres (1,434 ft), the highest point in the parish) along the western coast to Lhiattee ny Beinnee, Bradda Hill, Mull Hill, and the Sound, across which the ridge continues onto the Calf.

Rushen was repurposed as a detention camp during World War II, accommodating over 3,500 women and children.

These internees, considered "enemy aliens," included many refugees who had previously fled persecution in Europe.