The Aire River rises below the Otway Ranges in a remote forestry area southeast of the locality of Beech Forest. The river generally flows west by south then south through the Great Otway National Park, joined by three minor tributaries, before reaching its mouth and emptying into Bass Strait west of Cape Otway.[4][5][6] The river descends 555 metres (1,821 ft) over its 40 kilometres (25 mi) course;[3] including a 49 metres (161 ft) descent over the Hopetoun Falls in its upper reaches, located at an elevation of 314 metres (1,030 ft) above sea level.[7]