The Swanfleet (or Nîn-in-Eilph in Sindarin) was a marshy area in Eriador. Formed where the Glanduin (mistakenly labelled as "Swanfleet river" on some maps) joined the Mitheithel (Greyflood), the Swanfleet was effectively an inland delta, with uncertain streams and a very uncertain difference between land and water. It was about fifty miles in length from west to east and over twenty-five miles from north and south.