The Elwynn is a prominent river system running through Eastern Benacia. It is the largest and longest river of Benacia, and is one of the longest rivers of Micras. The river consists of two major arms, the Blue Elwynn (the western arm) and the White Elwynn (the eastern arm), which meander slowly southwards until they flow together east of Shirekeep and become the Red Elwynn, which from that point on continues to meander slowly southwards to the Elwynn River Delta, passing the Gates of the Guttuli, where it flows into the Shire Sea. Numerous other tributaries feed the river system. Most of the length of the Elwynn and its tributaries are under the control and sovereignty of the Benacian Union, while the confluence of the Blue and Red Elwynns, as well as the mouth and delta of the combined Elwynn by Guttuli are under the control of Shireroth.
The length of the Red Elwynn is, from the confluence of the Blue Elwynn and the White Elwynn east of the City of Shirekeep, 2660 km. The total combined length of the Blue Elwynn and the Red Elwynn is 5170 km; the total combined length of the White Elwynn and the Red Elwynn is 4590 km.
The Elwynn is traditionally held to have been named after the goddess Elwynn who, in Treesian mythology, resided in the Tower of Araxion close to one source of the Blue Elwynn. It has since given name to the country of Elwynn.
The Elw people, natively residing between the Blue and White Elwynns, claim that the river system is named after them.
The major tributaries of the Blue Elwynn are, from north to south, the:
- Araxionian Elwynn. Source near the legendary Tower of Araxion and is considered holy in branches of the Treesianoid religions.
- Kilkadeshi Elwynn. The source of this river is situated near Kilkadesh.
- Mishalanski Elwynn or Mishalense Elwynn or Mudyy River (Mishalanese: Mudyy), source is to be found in the east of the continental part of Mishalan.
The major tributaries of the White Elwynn are the:
- Aiomidean Elwynn: This tributary flow has its source west of Eliria;
- Elirian Elwynn: This river has its source immediately north and east of Eliria
- Fenririan Elwynn or the Fenrir. A river of which the source is to be found east of the Fenririe;
- Hol Elwynn, or the Holwinn ( alsoknown in the Istanistani language as the Kingsweep Tributary) The natural spring that serves as the source of this river is situated north of the old Suthergold-Holwinn border.