The main part of this article relates to the version of Middle-earth's history that is considered canon by most Tolkien fans who accept such labels (see: Middle-earth canon). This subject's portrayal in earlier or alternative versions is discussed in the other versions of the legendarium section.

In J. R. R. Tolkien's Middle-earth legendarium, the Beleriand river Taeglin was a tributary of Sirion.

It rose in the Ered Wethrin and flowed southeast through Brethil to join Sirion on the borders of Doriath.

An important for on the river was the Crossings of Teiglin, near the western border of Brethil. A road ran through it from Nargothrond to Minas Tirith.

Minor tributaries were Celebros and Malduin.

Other versions of the legendarium

In earlier writings, the river was called Teiglin. As revealed in the History of Middle-earth series, the rivername should actually have been spelt Taeglin. This was a relatively late change which was not adopted into the published Silmarillion, which uses the old name.