Glanduin

The river Glanduin was a river of Eriador and a northern arm of the Gwathló.

Beginning in the Hithaeglir south of Khazad-dûm, it flowed west-north-west until it was met by the Sirannon near the old location of Ost-in-Edhil, the capital of the Noldor of Eregion. From there the Glanduin flowed towards the Mitheithel, which it met in the marshes known as Swanfleet or Nîn-in-Eilph north-east of Tharbad. From there on both rivers became the Gwathló.

On some versions of the Middle-earth map the name Swanfleet appears to be an alternative name for the river, but in fact the name apparently refers to the marshes alone.