Alonnah (Australian Postcode 7150) is a small township on the western side of Bruny Island, Tasmania, facing the D'Entrecasteaux Channel. Originally named Mill's Reef, it was renamed in the early 1900s after part of the Tasmanian aboriginal name for Bruny Island, Lunawanna-alonnah (a nearby township a little to its south being named Lunawanna. At the 2006 census, Alonnah had a population of 302.[1]