The Styx River is a perennial river that is located in the centre of southern Tasmania, Australia. The upper reaches of the Styx River are located in the Tasmanian Wilderness, south west of Maydena. The river is a popular destination for river-rafting and canoeing.
The Styx River rises below Mount Mueller at an elevation of 1,110 metres (3,640 ft) above sea level and flows generally east by north, joined by five minor tributaries, before reaching its confluence with the River Derwent near Macquarie Plains, west of New Norfolk. The river descends 1,090 metres (3,580 ft) over its 59-kilometre (37 mi) course.