The Acheron River is a river in the South Island of New Zealand, in Marlborough and flows into the Waiau Toa / Clarence River. It flows southwest and then east for a total of , joining the Waiau Toa / Clarence at the southern end of the Inland Kaikōura mountains. The Alma and Severn Rivers flow into the Acheron before it joins the Waiau Toa / Clarence.
See also
- List of rivers of New Zealand
- Acheron River (Canterbury)
- Acheron (river in Greece)