[1] It is a small township on the western side of Bruny Island, facing the D'Entrecasteaux Channel.

Alonnah is the main location in Bruny Island for government facilities, including post office, police station, primary school, internet centre, community library, pharmacy, and health centre with nurses, a visiting doctor, physiotherapist, and other health practitioners.

There is also a museum located in the court house, Bruny Hotel, and a small general store.

Mill's Reef Post Office opened on 1 February 1905 and was renamed Alonnah in 1909.

[4] Route B66 (Bruny Island Main Road) runs through from south-west to east.