Port MacDonnell is a small port about 470 km southeast of Adelaide (28 km south of Mount Gambier), in South Australia. Port MacDonnell is the southernmost town in South Australia. The area was originally inhabited by the Bungandidj Aborigines.
The first Europeans to see the area were led by explorer Lieutenant James Grant in the HMS Lady Nelson on the 3 December 1800. It was surveyed and named in 1860 when it was proclaimed an official port. It is named after Sir Richard Graves MacDonnell who was Governor of South Australia from 1855 to 1862.
Port MacDonnell is in the District Council of Grant local government area, the South Australian House of Assembly electoral district of Mount Gambier and the Australian House of Representatives Division of Barker.